Polyimides as dielectric

ABSTRACT

The present invention provides a process for the preparation of a transistor on a substrate, which transistor comprises a layer, which layer comprises polyimide B, which process comprises the steps of
         i) forming a layer comprising photocurable polyimide A by applying photocurable polyimide A on a layer of the transistor or on the substrate   ii) irradiating the layer comprising photocurable polyimide A with light of a wavelength of &gt;=360 nm in order to form the layer comprising polyimide B,
 
and a transistor obtainable by that process.

The present invention relates to a process for the preparation of atransistor on a substrate and to a transistor on a substrate obtainableby that process.

Transistors, and in particular organic field-effect transistors (OFETs),are used as components for organic light emitting display, e-paper,liquid crystal display and radiofrequency identification tags.

An organic field effect transistor (OFET) comprises a semiconductinglayer comprising an organic semiconducting material, a dielectric layercomprising a dielectric material, a gate electrode and source/drainelectrodes.

Organic field effect transistors (OFETs), wherein the dielectricmaterial is an organic dielectric material, which can be applied bysolution processing techniques, are de-sired. Solution processingtechniques are convenient from the point of processability, and can alsobe applied to plastic substrates. Thus, organic dielectric materials,which are compatible with solution processing techniques, allow theproduction of low cost organic field effect transistors on flexiblesubstrates.

Polyimides are suitable organic dielectric material for use in organicfield effect transistors (OFET). Organic field effect transistors(OFET), wherein the dielectric material is a polyimide, are known in theart.

Kato, Y.; Iba, S.; Teramoto, R.; Sekitani, T.; Someya, T., Appl. Phys.Lett. 2004, 84(19), 3789 to 3791 describes a Bottom-Gate Bottom-Contactorganic field-effect transistors (OFET) comprising a pentacene top layer(semiconducting layer), a polyimide layer (dielectric gate layer) and apolyethylenenapthalate (PEN) base film (substrate).

The transistor is prepared using a process which comprises the followingsteps: (i) evaporating gate electrodes consisting of gold and chromiumlayers through a shadow mask on 125 μm thick PEN film in a vacuumsystem, (ii) spin-coating a polyimide precursor on the PEN base film andevaporating the solvent at 90° C., (iii) curing the polyimide precursorat 180° C. to obtain a polyimide gate dielectric layer, (iv) sublimingpentacene through a shadow mask at ambient temperature on the polyimidegate di-electric layer, and (v) evaporating source-drain electrodesconsisting of gold layers through a shadow mask. A transistor with a 990nm polyimide gate dielectric layer shows a channel length (L) of 100 μm,a width (W) of 1.9 mm, an on/off ratio of 10⁶ (if the source draincurrent (I_(DS)) at gate voltage (V_(GS)) is 35 V) and a mobility of 0.3cm²/Vs. The leakage current density of capacitors comprising a 540 nmthick polyimide layer between two gold electrodes is less than 0.1nA/cm² at 40 V and less than 1.1 nA/cm² at 100 V.

Lee, J. H.; Kim, J. Y.; Yi, M. H.; Ka, J. W.; Hwang, T. S.; Ahn, T. Mol.Cryst. Liq. Cryst. 2005, 519, 192-198 describes a Bottom-GateBottom-Contact organic field-effect transistor comprising a pentacenetop layer (semiconducting layer), a cross-linked polyimide layer(dielectric gate layer) and glass (substrate). The transistor isprepared using a process which comprises the following steps: (i)patterning indium tin oxide of indium tin oxide coated glass as 2 mmwide stripes to obtain glass with indium tin oxide gate electrodes, (ii)spin-coating a solution of hydroxyl group containing polyimide (preparedby reacting 2,2-bis-(3,4-dicarboxyphenyl)hexafluoropropane dianhydrideand 3,3′-dihydroxy-4,4′-diaminobiphenyl), trimethylolpropane triglycidylether, benzoyl peroxide and triphenylsulfonium triflate as photoacid inγ-butyrolactone on the glass with the indium tin oxide gate electrodesand evaporating the solvent at 100° C., (iii) crosslinking the hydroxylgroup containing polyimide and trimethylolpropane triglycidyl ether byexposure to UV light followed by hardening at 160° C. for 30 minutes toobtain a 300 nm thick polyimide gate dielectric layer, (iv) depositingon top of the gate dielectric layer a 60 nm thick pentacene layerthrough a shadow mask using thermal evaporation at a pressure of 1×10⁻⁶torr, and (v) evaporating source-drain gold electrodes on top of thepentacene layer. The transistor so produced shows a channel length (L)of 50 μm, a width (W) of 1.0 mm, an on/off ratio of 1.55×10⁵ and amobility of 0.203 cm²/Vs. The leakage current density of capacitorsconsisting of a 300 nm thick cross-linked polyimide layer between twogold electrodes is less than 2.33×10⁻¹⁰ A/cm² at 3.3 A/cm² indicatingthat the dielectric layer is resistant to moisture and otherenvironmental conditions.

Pyo, S.; Lee, M.; Jeon, J.; Lee, J. H.; Yi, M. H.; Kim, J. S. Adv.Funct. Mater. 2005, 15(4), 619 to 626 describes a Bottom-gateBottom-contact organic field-effect transistor comprising a pentacenetop layer (semiconducting layer), a patterned polyimide layer (preparedfrom 3,3′,4,4′-benzophenone tetracarboxylic dianhydride (BTDA) and7-(3,5-diaminobenzoyloxy)coumarine) (dielectric gate layer) and glass(substrate). The transistor is prepared using a process which comprisesthe following steps: (i) depositing gold electrodes through a shadowmask by thermal evaporation on the glass substrate (ii) spin-coating theprecursor of the polyimide (namely the poly(amic acid)) on top of thegate electrode and baking at 90° C. for 2 minutes, (iii) crosslinkingparts of the poly(amic acid) film by irradiating with UV light at 280 to310 nm through a mask followed by post-exposure baking at 160° C. for 19minutes, (iv) removing the not cross-linked parts of the poly(amic acid)film by dipping into aqueous tetramethylammonium hydroxide solutionfollowed by rinsing with water, (v) thermally converting the patternedcrosslinked poly(amic acid) film obtained in step (iv) to a patternedpolyimide layer (300 nm thick) by baking at 250° C. for 1 minute, (vi)depositing a 60 nm thick pentacene layer on top of the polyimide filmthrough a shadow mask by thermal evaporation, and (vii) thermallyevaporating gold source and drain electrodes on top of the pentacenelayer through a shadow mask. The leakage current density of capacitorsconsisting of a polyimide layer between two gold electrodes is less than1.4×10⁻⁷ A/cm². The breakdown voltage of this gate insulator was morethan 2 MV cm⁻¹. The capacitance of the film was found to be 129 pF/mm².The patterned polyimde layer allows the creation of access to the gateelectrode.

KR 2008-0074417 A (application date: 9 Feb. 2007, inventors: Yi, M. H.;Taek, A.; Sun, Y. H.) describes a low temperature soluble mixtureconsisting of two polyimides, which mixture is suitable as insulatinglayer in transistors. In both polyimides the group R (which is the groupcarrying the four carboxylic acid functionalities forming the two imidegroups) is at least one tetravalent group including a specific aliphaticcyclic tetravalent group. In the second polyimide the group R² (which isthe group carrying the two amine functionalities forming the two imidegroups) is at least a divalent group including a divalent aromatic grouphaving a pendant alkyl group. Exemplified is, for example, a mixtureconsisting of polyimide SPI-3 (prepared from1-(3,5-diaminophenyl)-3-octadecyl-succinic imide and5-(2,5-dioxotetrahydrfuryl)-3-methylcyclohexane-1,2-di-carboxylicdianhydride) and polyimide SPI-1 (prepared from 4,4′-diaminodiphenyl-methane (or methylenedianiline) and5-(2,5-dioxotetrahydrfuryl)-3-methylcaclohexane-1,2-dicarboxylicdianhydride) in γ-butyrolactone and cyclohexanone. A transistor isprepared using a process which comprises the following steps: (i)deposing a gate electrode through a mask, (ii) spin-coating a polyimidemixture and drying at 90° C., (ii) baking at 150° C., (iii) depositingpentacene by vacuum evaporation, (iv) depositing source-drainelectrodes. As substrate glass and polyethersulfone is used.

Sim, K.; Choi, Y.; Kim, H.; Cho, S.; Yoon, S. C.; Pyo, S. OrganicElectronics 2009, 10, 506-510 describes a bottom gate organicfield-effect transistor comprising a6,13-bis-(triisopropyl-silylethynyl) pentacene (TIPS pentacene) toplayer (semiconducting layer), a low-temperature processable polyimidelayer (prepared from 3,3′,4,4′-benzophenone-tetracarboxylic dianhydride(BTDA) and 4,4′-diamino-3,3′-dimethyl-diphenylmethane (DADM))(dielectricgate layer) and glass (substrate). A transistor is prepared using aprocess which comprises the following steps: (i) photo-lithographicallypatterning indium tin oxide on a glass substrate, (ii) spin-coating asolution of BPDA-DADM polyimide in N-methylpyrrolidone (NMP) on top ofthe gate electrode, (iii) soft baking at 90° C. for 1 minute, (iv)further baking at 175° C. for 1 hour in vacuum, and (v) drop coating asolution of TIPS pentacene and a polymeric binder in o-dichloromethaneon the BPDA-DADM polyimide layer, (vi) baking at 90° C. for 1 hour invacuum, (vii) thermally evaporating 60 nm thick source and drain goldelectrodes through a shadow mask. The transistor so produced shows achannel length (L) of 50 μm, a width (W) of 3 mm, an on/off ratio of1.46×10⁶ and a mobility of 0.15 cm²/Vs.

Chou, W.-Y.; Kuo, C.-W.; Chang, C.-W.; Yeh, B.-L.; Chang, M.-H. J.Mater. Chem. 2010, 20, 5474 to 5480 describes a bottom gate organicfield-effect transistor comprising a pentacene top layer (semiconductinglayer), a photosensitive polyimide (prepared from 4,4′-oxydianiline(ODA), 4,4′-(1,3-phenylenedioxy)dianiline (TPE-Q),4-(10,13-di-methyl-17-(6-methylheptan-2-yl)-2,3,4,7,8,9,10,11,12,13,14,15,16,17-tetradecahydro-1H-cyclopenta[a]phenanthren-3-yloxy)benzene-1,3-diamine(CHDA), pyromellitic dianhydride (PDMA), andcyclobutane-1,2,3,4-tetracarboxylic dianhydride (CBDA)) layer(dielectric gate layer), a silicium dioxide layer (dielectric gatelayer) and heavily doped n-type silicium (111) wafer (gate andsubstrate). The photosensitive polyimide used only absorbs at awavelength of 250 to 300 nm. The transistor is prepared using a processwhich comprises the following steps: (i) plasma-enhanced chemical vapourdepositing a 300 nm thick silicium dioxide layer, (ii) spin-coating a 80nm thick photo-sensitive polyimide layer on the silicium dioxide layer,(iii) baking (removing the solvent of) the photosensitive polyimidelayer at 220° C. for 60 minutes, (iv) irradiating with UV light, (v)depositing a 70 nm thick pentacene layer onto the photosensitivepolyimide layer at room temperature by vacuum sublimation, and (vi)depositing silver source-drain electrodes on the pentacene film througha shadow mask. The transistor so produced shows a channel length (L) of120 μm, a width (W) of 1920 μm, an on/off ratio of 10³ to 10⁵ (dependingon the UV dose applied) and an average mobility of 6.0 cm²/Vs. Thesurface energy, surface carriers and capacitance of the polyimide gatedielectric can be tuned by varying irradiation doses of UV light on thephotosensitive polyimide surface.

KR 2010-0049999 A (application date: 13. May 2010, inventors: Ahn, T.;Yi, M. H.; Kim, J. Y.) describes two soluble photocurable polyimidessuitable for use as insulator in transistors. In both polyimides thegroup R (which is the group carrying the four carboxylic acidfunctionalities forming the two imide groups) is at least onetetravalent group including a specific aliphatic cyclic tetravalentgroup. In both polyimide the group R¹ (which is the group carrying thetwo amine functionalities forming the two imide groups) carries anoptionally substituted photocurable cinnamoyl group. For example, thepolyimide KPSPI-1 is prepared from5-(2,5-dioxotetrahydrfuryl)-3-methylcyclohexane-1,2-dicarboxylicdianhydride and 3,3-dihydroxybenzidine, followed by reaction withcinnamoyl chloride. The polyimide layer can be prepared by (i)spin-coating a 9 weight % solution of the photocurable polyimide(KPSPI-1) in γ-butyrolactone and baking at 90° C. for 10 minutes, (iii)curing by UV irradiation (300 to 400 nm), (iii) hard-baking at 160° C.for 30 minutes. The leakage current density of capacitors consisting ofthe photocured polyimide layer (KPSPI-1) between two gold electrodes is7.84×10⁻¹¹ A/cm². The breakdown voltage of KPSPI-1 is 3 MV cm⁻¹.

The disadvantage of above processes for the preparation of organic fieldeffect transistors having a dielectric layer comprising a polyimide isthat the formation of the dielectric layer requires temperatures of atleast 150° C. These high temperatures are not compliable with all kindsof plastic substrates, for example these temperatures are not compliablewith polycarbonate substrates, as polycarbonate has a glass temperature(Tg) of 150° C. and softens gradually above this temperature. However,polycarbonate is an ideal substrate for preparing thin and flexibleorganic field effect transistors.

Thus, it was the object of the present invention to provide a processfor the preparation of a transistor on a substrate, preferably anorganic field effect transistor, comprising a layer comprisingpolyimide, for example as dielectric layer, wherein the step of formingthe layer comprising polyimide is performed at temperatures below 160°C., preferably below 150°, more preferably below 120° C.

This object is solved by the process of claim 1, and the transistor ofclaim 15.

The process of the present invention for the preparation of a transistoron a substrate, which transistor comprises a layer, which layercomprises polyimide B, comprises the steps of

-   -   i) forming a layer comprising photocurable polyimide A by        applying photocurable polyimide A on a layer of the transistor        or on the substrate    -   ii) irradiating the layer comprising photocurable polyimide A        with light of a wavelength of >=360 nm in order to form the        layer comprising polyimide B.

Preferably, the process does not comprise a step of heat treatment at atemperature of >=160° C., More preferably, the process does not comprisea step of heat treatment at a temperature of >=150° C. Most preferably,the process does not comprise a step of heat treatment at a temperatureof >=120° C.

Preferably, the layer comprising photocurable polyimide A is irradiatedwith light of a wavelength of >=360 nm and <=440 nm in order to form thelayer comprising polyimide B. More preferably it is irradiated withlight of a wavelength of 365 nm, 405 nm and/or 435 nm. Most preferablyit is irradiated with light of a wavelength of 365 nm.

Preferably, the photocurable polyimide A is a photocurable polyimide,which carries (i) at least one photosensitive group, and (ii) at leastone crosslinkable group.

The photosensitive group is a group that generates a radical byirradiation with light of a wavelength of >=360 nm, preferably withlight of a wavelength of >=360 nm and <=440 nm, more preferably withlight of a wavelength of 365 nm, 405 nm and/or 435 nm, most preferablywith light of a wavelength of 365 nm.

The crosslinkable group is a group which is capable of generating aradical by reaction with the radical generated from the photosensitivegroup by irradiation with light of a wavelength of >=360 nm, preferablywith light of a wavelength of >=360 nm and <=440 nm, more preferablywith light of a wavelength of 365 nm, 405 nm and/or 435 nm, mostpreferably with light of a wavelength of 365 nm.

Preferably, the photocurable polyimide A is a polyimide which isobtainable by reacting a mixture of reactants, which mixture ofreactants comprise at least one dianhydride A, and at least one diamineA, wherein

-   -   (i) the dianhydride A is a dianhydride carrying at least one        photosensitive group and the diamine A is a diamine carrying at        least one crosslinkable group,    -   (ii) the dianhydride A is a dianhydride carrying at least one        crosslinkable group and the diamine A is an diamine carrying at        least one photosensitive group,    -   (iii) the dianhydride A is a dianhydride carrying at least one        photosensitive group and at least one crosslinkable group, or    -   (iv) the diamine A is a diamine carrying at least one        photosensitive group and at least one crosslinkable group,    -   wherein the photosensitive group and the crosslinkable group are        as defined above.

The dianhydride A is an organic compound carrying two —C(O)—O—C(O)—functionalities.

The diamine A is an organic compound carrying two amino functionalities.

Preferably, the mixture of reactants are reacted in a suitable solvent,such as N-methyl-pyrrolidone, tetrahydrofuran or 1,4-dioxane, at asuitable temperature, for example at a temperature in the range of 10 to150° C., or at a temperature in the range from 10 to 50° C., or at atemperature in the range from 18 to 30° C.

In a preferred embodiment, the photocurable polyimide A is a polyimidewhich is obtainable by reacting a mixture of reactants, which mixture ofreactants comprise at least one dianhydrides A and at least one diaminesA, wherein the dianhydride A is dianhydrides carrying at least onephotosensitive group and the diamines A is a diamine carrying at leastone crosslinkable group, wherein the photosensitive group and thecrosslinkable group are as defined above.

Preferably, the dianhydride A, which is dianhydrides carrying at leastone photosensitive group, is a benzophenone derivative carrying two—C(O)—O—C(O)— functionalities.

More preferably, the dianhydrides A, which is a dianhydrides carrying atleast one photosensitive group, is a benzophenone derivative carryingtwo —C(O)—O—C(O)— functionalities, wherein the two —C(O)—O—C(O)—functionalities are directly attached to the same or to different phenylrings of the benzophenone basic structure.

More preferably, the dianhydride A which is a dianhydride carrying atleast one photo-sensitive group, is selected from the group consistingof

whereinR¹ is C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, halogen or phenylg is 0, 1, 2 or 3, preferably 0,X is a direct bond, CH₂, O, S or C(O), preferably X is a direct bond,CH₂ or O.

Even more preferably, the dianhydride A which is a dianhydride carryingat least one photosensitive group, is selected from the group consistingof

wherein X can be O, S and CH₂.

Examples of the dianhydride of formula (2a) are the dianhydrides offormulae

The most preferred dianhydride A, which is a dianhyride carrying atleast one photo-sensitive group, is the dianhydride of formula

Dianhydrides of formulae (1), (2), (3) and (4) can either be prepared bymethods known in the art or are commercially available. For example,dianhydride (2a1) can be prepared as described in EP 0 181 837, exampleb, dianhydride (2a2) can be prepared as described in EP 0 181 837 A2,example a. Dianhydride (1a) is commercially available.

Preferably, the diamine A, which is a diamine carrying at least onecrosslinkable group, is an organic compound carrying

(i) two amino functionalities,and(iia) at least one aromatic ring having attached at least one CH₂ or CH₃group or(iib) at least one carbon-to-carbon double bond having attached at leastone H, or at least one CH₂ or CH₃ group.

Alternative (iia) is preferred to alternative (iib).

Examples of aromatic rings are phenyl and naphthyl. Phenyl is preferred.

More preferably the diamine A, which is a diamine carrying at least onecrosslinkable group, is selected from the group consisting of

(i) a diamine of formula

whereinR², R³ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkyl,n is 1, 2, 3 or 4m is 0, 1, 2 or 3provided n+m<=4,p is 0, 1, 2, 3 or 4,L¹ is O, S, C₁₋₁₀-alkylene, phenylene or C(O)wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S,(ii) a diamine of formula

whereinR⁴ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkylR⁵ is O—C₁₋₁₀-alkyl, O—C₁₋₁₀-alkylene-O—C₁₋₁₀-alkyl,O—C₁₋₁₀-alkylene-N(C₁₋₁₀-alkyl)₂, N(C₁₋₁₀-alkyl)₂, O-phenyl, W,O—C₁₋₁₀-alkylene-W, O-phenylene-W, N(R⁶)(C₁₋₁₀-alkylene-W) orN(R⁶)(phenylene-W),

-   -   wherein    -   R⁶ is H, C₁₋₁₀-alkyl, C₄₋₁₀-cycloalkyl or C₁₋₁₀-alkylene-W,    -   W is O—C₂₋₁₀-alkenyl, N(R⁷)(C₂₋₁₀-alkenyl), O—C(O)—CR⁶═CH₂,        N(R⁷)(C(O)—CR⁸═CH₂), or

-   -   wherein    -   R⁷ is H, C₁₋₁₀-alkyl, C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl or        C(O)—CR⁸═CH₂,    -   R⁸ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl,    -   R⁹ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl        q is 1, 2, 3 or 4        o is 0, 1, 2, 3        q+o<=4,        in case o is 0, R⁵ is W, O—C₁₋₁₀-alkylene-W, O-phenylene-W,        N(R⁸)(C₁₋₁₀-alkylene-W) or N(R⁶)(phenylene-W),        wherein C₁₋₁₀-alkylene, can be optionally substituted with one        or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, and/or C₄₋₈-cycloalkyl, or        interrupted by O or S,        and        (iii) a diamine of formula

whereinR¹⁰ and R¹¹ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkylR¹³ and R¹⁴ are the same and different and are C₁₋₁₀-alkyl,C₁₋₁₀-haloalkyl, C₄₋₈-cycloalkyl, phenyl, C₂₋₁₀-alkenyl orC₄₋₁₀-cycloalkenyl,L² is C₁₋₁₀-alkylene or phenylener is 0, 1, 2, 3 or 4s is 0, 1, 2, 3 or 4r+s<=4in case both r and s are 0 then at least one of R¹³ and R¹⁴ isC₂₋₁₀-alkenyl or C₄₋₁₀-cycloalkenyl,t is 0, 1, 2, 3, 4 or 5u is 0 or 1wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or C₁₋₁₀-alkylenecan be optionally interrupted by O or S.

Examples of halogen are fluoro, chloro and bromo.

Examples of C₁₋₁₀-alkyl are methyl, ethyl, propyl, isopropyl, butyl,sec-butyl, isobutyl, tert-butyl, pentyl, 2-ethylbutyl, hexyl, heptyl,octyl, nonyl and decyl. Examples of C₁₋₄-alkyl are methyl, ethyl,propyl, isopropyl, butyl, sec-butyl, isobutyl and tert-butyl.

Examples of C₄₋₈-cycloalkyl are cyclobutyl, cyclopentyl, cyclohexyl,cycloheptyl and cyclooctyl.

Examples of C₁₋₁₀-haloalkyl are trifluoromethyl and pentafluoroethyl.

Examples of C₂₋₁₀-alkenyl are vinyl, CH₂—CH═CH₂, CH₂—CH₂—CH═CH₂.

Examples of C₄₋₁₀-cycloalkenyl are cyclopentyl, cyclohexyl andnorbornenyl.

Examples of C₁₋₁₀-alkylene are methylene, ethylene, propylene, butylene,pentylene, hexylene and heptylene. Examples of C₁₋₄-alkylene aremethylene, ethylene, propylene and butylene

Examples of C₄₋₈-cycloalkylene are cyclobutylene, cyclopentylene,cyclohexylene and cycloheptylene.

Examples of C₁₋₄-alkanoic acid are acetic acid, propionic acid andbutyric acid.

The diamine of formula (5) is preferred to the diamines of formulae (6)and (8).

Preferred diamines of formula (5) are diamines of formula

whereinR², R³ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkyl,n is 1, 2, 3 or 4m is 0, 1, 2 or 3provided n+m<=4,p is 0, 1, 2, 3 or 4,L¹ is O, S, C₁₋₁₀-alkylene, phenylene or C(O)wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.

Examples of diamines of formula (5a) are

In preferred diamines of formula (5a)

R², R³ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkyl,n is 1, 2, 3m is 0, 1, 2provided n+m=2, 3 or 4p is 0, 1, 2, 3 or 4,L¹ is O, S or C₁₋₁₀-alkylene wherein C₁₋₁₀-alkylene can be optionallysubstituted with one or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/orC₄₋₈-cycloalkyl.

In more preferred diamines of formula (5a)

R², R³ are the same or different and are C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl,n is 1, 2,m is 0, 1,provided n+m=2p is 1,L¹ is O or C₁₋₁₀-alkylene.

In even more preferred diamines of formula (5a)

R² is C₁₋₄alkyl,n is 2,p is 1,L¹ is O or C₁₋₄-alkylene.

The most preferred diamines of formula (5a) is the diamine of formula

The diamines of formula (5) are either commercially available or can beprepared by methods known in the art, for example as described for thediamine of formula (5a4) in Oleinik, I. I.; Oleinik, I. V.; Ivanchev, S.S.; Tolstikov, G. G. Russian J. Org. Chem. 2009, 45, 4, 528 to 535.

A preferred diamine of formula (6) is a diamine of formula

whereinR⁴ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkylR⁵ is O—C₁₋₁₀-alkyl, O—C₁₋₁₀-alkylene-O—C₁₋₁₀-alkyl,O—C₁₋₁₀-alkylene-N(C₁₋₁₀-alkyl)₂, N(C₁₋₁₀-alkyl)₂, O-phenyl, W,O—C₁₋₁₀-alkylene-W, O-phenylene-W, N(R⁶)(C₁₋₁₀-alkylene-W) orN(R⁶)(phenylene-W),

-   -   wherein    -   R⁶ is H, C₁₋₁₀-alkyl, C₄₋₁₀-cycloalkyl or C₁₋₁₀-alkylene-W,    -   W is O—C₂₋₁₀-alkenyl, N(R⁷)(C₂₋₁₀-alkenyl), O—C(O)—CR⁸═CH₂,        N(R⁷)(C(O)—CR⁸═CH₂), or

-   -   -   wherein        -   R⁷ is H, C₁₋₁₀-alkyl, C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl or            C(O)—CR⁸═CH₂,        -   R⁸ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl,        -   R⁹ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl            q is 1, 2, 3 or 4            o is 0, 1, 2, 3            q+o<=4,            in case o is 0, R⁵ is W, O—C₁₋₁₀-alkylene-W, O-phenylene-W,            N(R⁶)(C₁₋₁₀-alkylene-W) or N(R⁶)(phenylene-W),            wherein C₁₋₁₀-alkylene, can be optionally substituted with            one or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, and/or            C₄₋₈-cycloalkyl, or interrupted by O or S.

In preferred diamines of formula 6a

o is 0R⁵ is W, O—C₁₋₁₀-alkylene-W, O-phenylene-W, N(R⁶)(C₁₋₁₀-alkylene-W) orN(R⁶)(phenylene-W),

-   -   wherein    -   R⁶ is H, C₁₋₁₀-alkyl, C₄₋₁₀-cycloalkyl or C₁₋₁₀-alkylene-W,    -   W is O—C₂₋₁₀-alkenyl, N(R⁷)(C₂₋₁₀-alkenyl), O—C(O)—CR⁸═CH₂,    -   N(R⁷)(C(O)—CR⁸═CH₂), or

-   -   -   wherein        -   R⁷ is H, C₁₋₁₀-alkyl, C₄₋₈cycloalkyl, C₂₋₁₀-alkenyl or            C(O)—CR⁸═CH₂,        -   R⁸ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl,        -   R⁹ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl            q is 1 or 2            wherein C₁₋₁₀-alkylene, can be optionally substituted with            one or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, and/or            C₄₋₈-cycloalkyl, or interrupted by O or S.

In more preferred diamines of formula 6a

o is 0R⁵ is O—C₁₋₁₀-alkylene-W or O-phenylene-W

-   -   wherein    -   W is O—C₂₋₁₀-alkenyl, N(R⁷)(C₂₋₁₀-alkenyl), O—C(O)—CR⁸═CH₂,    -   N(R⁷)(C(O)—CR⁸═CH₂), or

-   -   -   wherein        -   R⁷ is H, C₁₋₁₀-alkyl, C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl or            C(O)—CR⁸═CH₂,        -   R⁸ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl,        -   R⁹ is C₁₋₁₀-alkyl,            q is 1            wherein C₁₋₁₀-alkylene, can be optionally substituted with            one or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, and/or            C₄₋₈-cycloalkyl, or interrupted by O or S.

In most preferred diamines of formula 6a

o is 0R⁵ is O—C₁₋₁₀-alkylene-W or O-phenylene-W

-   -   wherein    -   W is

-   -   -   wherein        -   R⁹ is methyl,            q is 1            wherein C₁₋₁₀-alkylene, can be optionally substituted with            one or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, and/or            C₄₋₈-cycloalkyl, or interrupted by O or S.

The most preferred diamine of formula 6a are the diamines of formulae

The diamines of formula (6) are either commercially available or can beprepared by methods known in the art. For example, the diamine offormula (6) can be prepared by reacting a dinitrocompound of formula(17) with H—R⁵, followed by reduction of the nitro groups.

A preferred diamine of formula (8) is the diamine of formula

whereinR¹⁰ and R¹¹ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkylR¹³ and R¹⁴ are the same and different and are C₁₋₁₀-alkyl,C₁₋₁₀-haloalkyl, C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl, C₄₋₁₀-cycloalkenyl orphenyl, L² is C₁₋₁₀-alkylene or phenylener is 0, 1, 2, 3 or 4s is 0, 1, 2, 3 or 4r+s<=4in case both r and s are 0 then at least one of R¹³ and R¹⁴ isC₂₋₁₀-alkenyl or C₄₋₁₀-cycloalkenyl,t is 0 or an integer from 0 to 50, preferably 0 or an integer from 0 to25, more preferably 0 or an integer from 1 to 6, most preferably 0 or 1,u is 0 or 1wherein C₁₋₁₀-alkylene, can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, and/or C₄₋₈-cycloalkyl, or interrupted byO or S.

Preferred diamines of formula (8a) are diamines of formulae

whereinR¹⁰ and R¹¹ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkyl R¹³ and R¹⁴ are the same and different and areC₁₋₁₀-alkyl, C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl, C₄₋₁₀-cycloalkenyl orphenyl,r is 0, 1, 2, 3 or 4s is 0, 1, 2, 3 or 4r+s<=4in case both r and s are 0 then at least one of R¹³ and R¹⁴ isC₂₋₁₀-alkenyl or C₄₋₁₀-cycloalkenyl,and

whereinR¹⁰ and R¹¹ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkylR¹³ and R¹⁴ are the same and different and are C₁₋₁₀-alkyl,C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl, C₄₋₁₀-cycloalkenyl or phenylL² is C₁₋₁₀-alkylener is 0, 1, 2, 3 or 4s is 0, 1, 2, 3 or 4r+s<=4in case both r and s are 0 then at least one of R¹³ and R¹⁴ isC₂₋₁₀-alkenyl or C₄₋₁₀-cycloalkenyl,t is 0 or an integer from 0 to 50, preferably 0 or an integer from 0 to25, more preferably 0 or an integer from 1 to 6, most preferably 0 or 1,wherein C₁₋₁₀-alkylene, can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, and/or C₄₋₈-cycloalkyl, or interrupted byO or S.

Examples of diamines of formula (8aa) are

An example of a diamine of formula (8ab) is the diamine of formula

Diamines of formula (8) are either commercially available or can beprepared by methods known in the art, for example diamines of formula(8aa) can be prepared as de-scribed by Ismail, R. M. Helv. Chim. Acta1964, 47, 2405 to 2410, examples 12 to 14, for example diamines offormula (8ab) can be prepared as described in EP 0 054 426 A2, forexample in examples XXVI and XXVIII.

The mixture of reactants can comprise at least one dianhydride B and/orat least one diamine B, wherein the dianhydride B can be any dianhydrideB different from dianhydride A and the diamine B can be any diamine Bdifferent from diamine A.

The dianhydride B is an organic compound carrying two —C(O)—O—C(O)—functionalities.

The diamine B is an organic compound carrying two amino functionalities.

In case the photocurable polyimide A is a polyimide which is obtainableby reacting a mixture of reactants, which mixture of reactants compriseat least one dianhydride A and at least one diamine A, wherein thedianhydride A is a dianhyride carrying at least one photosensitive groupand the diamine A is a diamine carrying at least one crosslinkablegroup, the dianhydride B is a dianhydride carrying no photosensitivegroup, and the diamine B is a diamine carrying no crosslinkable group,wherein the photosensitive group and the crosslinkable group are asdefined above.

Preferably, dianhydride B, which is a dianhydride carrying nophotosensitive group, is an organic compound containing at least onearomatic ring and carrying two —C(O)—O—C(O)— functionalities, whereinthe two —C(O)—O—C(O)— functionalities are attached to the same ordifferent aromatic rings.

More preferably, the dianhydride B, which is a dianhydride carrying nophotosensitive group, is selected from the group consisting of

whereinR¹² is C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, halogen or phenylh is 0, 1, 2 or 3, preferably 0,Y is a C₁₋₁₀-alkylene, O or S, preferably Y is CH₂ or O.

Even more preferably, the dianhydride B, which is a dianhydride carryingno photosensitive group, is selected from the group consisting of

Most preferably, the dianhydride B, which is a dianhydride carrying nophotosensitive group, is

The dianhydride B of formulae (9) to (12) are either commerciallyavailable or can be prepared by methods known in the art, for example bytreatment of the corresponding tetramethyl derivative with HNO₃ at 180°C.

The diamine B, which is a diamine carrying no crosslinkable group, canbe selected from the group consisting of

(i) a diamine of formula

whereinR¹⁵ is halogen or O—C₁₋₁₀-alkyl,d is 0, 1, 2, 3 or 4v is 0, 1, 2, 3 or 4,L³ is a direct bond, O, S, C₁₋₁₀-alkylene or CO,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S,(ii) a diamine of formula

whereinR¹⁶ is halogen or O—C₁₋₁₀-alkylR¹⁷ is O—C₁₋₁₀-alkyl, O—C₁₋₁₀-alkylene-O—C₁₋₁₀-alkyl, O-phenyl,O—C₁₋₁₀-alkylene-N(C₁₋₁₀-alkyl)₂ or N(C₁₋₁₀-alkyl)₂w is 0, 1, 2 or 3x is 1, 2, 3, 4w+x<=4,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S,(iii) a diamine of formula

whereinR¹⁸ is halogen or O—C₁₋₁₀-alkyl,R¹⁹ and R²⁰ are the same and different and are C₁₋₁₀-alkyl,C₁₋₁₀-haloalkyl or C₄₋₈-cycloalkyl or phenyl,L³ is C₁₋₁₀-alkylene or phenyleney is 0, 1, 2, 3 or 4z is 0 or 1a is 0 or an integer from 1 to 50, preferably 0 or an integer from 1 to25,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S,and(iv) a diamine of formula

whereinR²¹ and R²² are the same and different and are C₁₋₁₀-alkyl,C₁₋₁₀-haloalkyl or C₄₋₈-cycloalkyl,L⁴ is C₁₋₁₀-alkylene, C₄₋₈-cycloalkylene orC₄₋₈-cycloalkylene-Z—C₄₋₈-cycloalkylene,

-   -   wherein Z is C₁₋₁₀-alkylene, S, O or CO        b is 0 or 1        c is 0 or an integer from 1 to 50, preferably, 0 or an integer        from 1 to 25, more preferably 0 or an integer from 1 to 6, most        preferably 0 or 1        e is 0 or 1        wherein C₁₋₁₀-alkylene can be optionally substituted with one or        more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or        interrupted by O or S.

Preferably, diamine B, which is a diamine carrying no crosslinkablegroup, is a diamine of formula (14) or (16).

A preferred diamine of formula (13) a diamine of formula

whereinR¹⁵ is halogen or O—C₁₋₁₀-alkyl,d is 0, 1, 2, 3 or 4v is 0, 1, 2, 3 or 4,L³ is a direct bond, O, S, C₁₋₁₀-alkylene or CO,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.

Examples of diamines of formula 13a are

In preferred diamines of formula (13a)

d is 0, 1 or 2v is 1L³ is O or C₁₋₁₀-alkylene,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted byO.

In more preferred diamines of formula (13a)

d is 0v is 1L³ is 0 or methylene,wherein methylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl.

The diamines of formula (13) are either commercially available or can beprepared by methods known in the art, for example as described inIngold, C. K.; Kidd, H. V. J. Chem. Soc. 1933, 984 to 988.

A preferred diamine of formula (14) is the diamine of formula

whereinR¹⁶ is halogen or O—C₁₋₁₀-alkylR¹⁷ is O—C₁₋₁₀-alkyl, O—C₁₋₁₀-alkylene-O—C₁₋₁₀-alkyl, O-phenyl,O—C₁₋₁₀-alkylene-N(C₁₋₁₀-alkyl)₂ or N(C₁₋₁₀-alkyl)₂w is 0, 1, 2 or 3x is 1, 2, 3, 4w+x<=4,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.

Examples of diamines of formula (14a) are

In preferred diamines of formula (14a)

R¹⁶ is halogen or O—C₁₋₁₀-alkylR¹⁷ is O—C₁₋₁₀-alkyl, O—C₁₋₁₀-alkylene-O—C₁₋₁₀-alkyl or O-phenylw is 0, 1, 2 or 3x is 1.

In more preferred diamines of formula (14a)

R¹⁶ is halogen or O—C₁₋₁₀-alkylR¹⁷ is O—C₁₋₁₀-alkylw is 0, 1 or 2x is 1.

The most preferred diamines of formula (14a) is the diamine of formula

The diamines of formula (14) are either commercially available or can beprepared by methods known in the art.

For example, the diamine of formula (14) can be prepared by reacting adinitrocompound of formula (19) with H—R¹⁷, followed by reduction of thenitro groups.

Preferred diamines of formula (15) are diamines of formula

whereinR¹⁸ is halogen or O—C₁₋₁₀-alkyl,R¹⁹ and R²⁰ are the same and different and are C₁₋₁₀-alkyl,C₁₋₁₀-haloalkyl orC₄₋₈-cycloalkyl or phenyl,L³ is C₁₋₁₀-alkylene or phenyleney is 0, 1, 2, 3 or 4z is 0 or 1a is 0 or an integer from 1 to 50, preferably 0 or an integer from 1 to25,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.

Preferred diamines of formula (15a) are the diamines of formulae

whereinR¹⁸ is halogen or O—C₁₋₁₀-alkyl,R¹⁹ and R²⁰ are the same and different and are C₁₋₁₀-alkyl,C₄₋₈-cycloalkyl or phenyl,y is 0, 1, 2, 3 or 4and

whereinR¹⁸ is halogen or O—C₁₋₁₀-alkyl,R¹⁹ and R²⁰ are the same and different and are C₁₋₁₀-alkyl,C₄₋₈-cyclobutyl or phenylL³ is C₁₋₁₀-alkylene or phenylene,a is 0 or an integer from 1 to 50, preferably 0 or an integer from 1 to25,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.

Examples of diamines of formula (15aa) are

An example of a diamine of formula (15ab) is

Diamines of formula (15) are either commercially available or can beprepared by methods known in the art, for example diamines of formula(15aa) can be prepared as described by Ismail, R. M. Helv. Chim. Acta1964, 47, 2405 to 2410, examples 12 to 14, for example diamines offormula (15ab) can be prepared as described in EP 0 054 426 A2, forexample in examples XXVI and XXVIII.

Preferred diamines of formula (16) are the diamines of formulae

whereine is 0L⁴ is C₁₋₁₀-alkylene, C₄₋₈-cycloalkylene orC₄₋₈-cycloalkylene-Z—C₄₋₈-cycloalkylene,wherein Z is a direct bond, C₁₋₁₀-alkylene or O,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.and

whereinR²¹ and R²² are the same and different and are C₁₋₁₀-alkyl,L⁴ is C₁₋₁₀-alkylene, C₄₋₈-cycloalkylene orC₄₋₈-cycloalkylene-Z—C₄₋₈-cycloalkylene,wherein Z is C₁₋₁₀-alkylene or O,e is 1c is 0 or an integer from 1 to 50, preferably, 0 or an integer from 1 to25, more preferably 0 or an integer from 1 to 6, most preferably 0 or 1,wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.

An example of a diamine of formula (16a) is

Examples of diamines of formula (16b) are

In preferred diamines of formula (16a)

e is 0L⁴ is C₁₋₄-alkylene, which C₁₋₄-alkylene can be optionally substitutedwith one or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl.

In more preferred diamines of formula (16a)

e is 0L⁴ is C₁₋₄-alkylene.

The most preferred diamine of formula (16a) is

In preferred diamines of formula (16b)

e is 1R²¹ and R²² are the same and different and are C₁₋₁₀-alkyl,L⁴ is C₁₋₁₀-alkylene,c is 0 or an integer from 1 to 6wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S.

In more preferred diamines of formula (16b) wherein

e is 1R²¹ and R²² are the same and different and are C₁₋₄-alkylL⁴ is C₁₋₄-alkylenec is 0 or 1wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by—O—.

In most preferred diamines of formula (16b) the diamine of formula

e is 1R²¹ and R²² are the same and different and are C₁₋₄-alkylL⁴ is C₁₋₄-alkylenec is 1

The most preferred diamine of formula (16b) is the diamine of formula

Diamines of formula (16) are either commercially available or can beprepared by methods known in the art, for example the diamine of formula(16b1) is commercially available.

The mixture of reactants can comprise at least one dianhydride C and/orat least one diamine C, wherein the dianhydride C can be any dianhydridedifferent from dianhydride A and dianhydride B, and the diamine C can beany diamine different from diamine A and diamine B.

The dianhydride C is an organic compound carrying two —C(O)—O—C(O)—functionalities.

Preferably, dianhydride C is an organic compound containing at least onearomatic ring and carrying two —C(O)—O—C(O)— functionalities, whereinthe two —C(O)—O—C(O)— functionalities are attached to the same ordifferent aromatic rings.

The diamine C is an organic compound carrying two amino functionalities.

Preferably, the mixture of reactants does not comprise a dianhydride,which is an organic compound carrying two —C(O)—O—C(O)— functionalities,wherein the two —C(O)—O—C(O)— functionalities are attached to analiphatic residue.

Examples of aliphatic residues are alicyclic rings, alkyl or alkyleneresidue.

Examples of alicyclic rings are C₄₋₈-cycloalkyl, C₄₋₁₀-cycloalkenyl andC₄₋₈-cycloalkylene. Examples of alkyl are C₁₋₁₀-alkyl. Examples ofalkylene are C₁₋₁₀-alkylene.

In particular, the mixture of reactants does not comprise a dianhydrideselected from the group consisting of

Preferably the mixture of reactants does not comprise a diamine carryingone or more-substituents of formulae

wherein R²³ to R³¹ are the same or different and are independently H,C₁₋₁₀-alkyl, CN or halogen, and i, j and k are the same or different andare 0 or an integer from 1 to 10.

The mixture of reactants can comprise

from 0.1 to 100% by mol of all dianhydride A based on the sum of molesof all dianhydrides A and B and Cfrom 0 to 99% by mol of all dianhydride B based on the sum of moles ofall dianhydrides A and B and Cfrom 0 to 99% by mol of all dianhydride C based on the sum of moles ofall dianhydrides A and B and Cfrom 0.1 to 100% by mol of all diamine A based on the sum of moles ofall diamines A and B and Cfrom 0 to 99% by mol of all diamine B based on the sum of moles of alldiamines A and B and Cfrom 0 to 99% by mol of all diamine C based on the sum of moles of alldiamines A and B and C,wherein molar ratio of (dianhydride A and dianhydride B and dianhydrideC)/(diamine A and diamine B and diamine C) is in the range of 150/100 to100/150, preferably, in the range of 130/100 to 100/70, more preferablyin the range of 120/100 to 100/80, and most preferably, in the range of110/100 to 100/90.

Preferably, the mixture of reactants comprises

from 20 to 100% by mol of all dianhydride A based on the sum of moles ofall dianhydrides A and B and Cfrom 0 to 80% by mol of all dianhydride B based on the sum of moles ofall dianhydrides A and B and Cfrom 0 to 80%, by mol of all dianhydride C based on the sum of moles ofall dianhydrides A and B and Cfrom 20 to 100%, by mol of all diamine A based on the sum of moles ofall diamines A and B and Cfrom 0 to 80% by mol of all diamine B based on the sum of moles of alldiamines A and B and Cfrom 0 to 80% by mol of all diamine C based on the sum of moles of alldiamines A and B and C,wherein molar ratio of (dianhydride A and dianhydride B and dianhydrideC)/(diamine A and diamine B and diamine C) is in the range of 130/100 to100/70, more preferably in the range of 120/100 to 100/80, and mostpreferably, in the range of 110/100 to 100/90.

The mixture of reactants can essentially consist of

from 0.1 to 100% by mol of all dianhydride A based on the sum of molesof all dianhydrides A and B and Cfrom 0 to 99% by mol of all dianhydride B based on the sum of moles ofall dianhydrides A and B and Cfrom 0 to 99% by mol of all dianhydride C based on the sum of moles ofall dianhydrides A and B and Cfrom 0.1 to 100% by mol of all diamine A based on the sum of moles ofall diamines A and B and Cfrom 0 to 99% by mol of all diamine B based on the sum of moles of alldiamines A and B and Cfrom 0 to 99% by mol of all diamine C based on the sum of moles of alldiamines A and B and C,wherein molar ratio of (dianhydride A and dianhydride B and dianhydrideC)/(diamine A and diamine B and diamine C) is in the range of 150/100 to100/150, preferably, in the range of 130/100 to 100/70, more preferablyin the range of 120/100 to 100/80, and most preferably, in the range of110/100 to 100/90.

Preferably, the mixture of reactants essentially consists of

from 20 to 100% by mol of all dianhydride A based on the sum of moles ofall dianhydrides A and B and Cfrom 0 to 80% by mol of all dianhydride B based on the sum of moles ofall dianhydrides A and B and Cfrom 0 to 80%, by mol of all dianhydride C based on the sum of moles ofall dianhydrides A and B and Cfrom 20 to 100%, by mol of all diamine A based on the sum of moles ofall diamines A and B and Cfrom 0 to 80% by mol of all diamine B based on the sum of moles of alldiamines A and B and Cfrom 0 to 80% by mol of all diamine C based on the sum of moles of alldiamines A and B and C,wherein molar ratio of (dianhydride A and dianhydride B and dianhydrideC)/(diamine A and diamine B and diamine C) is in the range of 130/100 to100/70, more preferably in the range of 120/100 to 100/80, and mostpreferably, in the range of 110/100 to 100/90.

The glass temperature of the photocurable polyimide A is preferablyabove 150° C., more preferably above 170° C., and more preferablybetween 170° C. and 300° C.

The molecular weight of the photocurable polyimide A can be in the rangeof 5,000 to 1,000,000 g/mol, preferably, in the range of 5,000 to 40,000g/mol, most preferably in the range of 5′000 to 20′000 g/mol.

Preferably, photocurable polyimide A is applied as a solution in anorganic solvent A on the layer of the transistor or on the substrate.

The organic solvent A can be any solvent (or solvent mixture) that candissolve at least 2% by weight, preferably at least 5% by weight, morepreferably, at least 8% by weight of the photocurable polyimide A basedon the weight of the solution of photocurable polyimide A.

The organic solvent A can be any solvent (or solvent mixture) that has aboiling point (at ambient pressure) of below 180° C., preferably below150° C., more preferably below 130° C.

Preferably, the organic solvent A is selected from the group consistingof N-methyl-pyrrolidone, C₄₋₈-cycloalkanone, C₁₋₄-alkyl-C(O)—C₁₋₄-alkyl,C₁₋₄-alkanoic acid C₁₋₄-alkyl ester, wherein the C₁₋₄-alkyl or theC₁₋₄-alkanoic acid can be substituted by hydroxyl or O—C₁₋₄-alkyl, andC₁₋₄-alkyl-O—C₁₋₄-alkylene-O—C₁₋₄-alkylene-O—C₁₋₄-alkyl, and mixturesthereof.

Examples of C₄₋₈-cycloalkanone are cyclopentanone and cyclohexanone.

Examples of C₁₋₄-alkyl-C(O)—C₁₋₄-alkyl are ethyl isopropyl ketone,methyl ethyl ketone and methyl isobutyl ketone.

Examples of C₁₋₄-alkanoic acid C₁₋₄-alkyl ester, wherein the C₁₋₄-alkylor the C₁₋₄-alkanoic acid can be substituted by hydroxyl orO—C₁₋₄-alkyl, are ethyl acetate, butyl acetate, isobutyl acetate,(2-methoxy)ethyl acetate, (2-methoxy)propyl acetate and ethyl lactate.

An example of C₁₋₄-alkyl-O—C₁₋₄-alkylene-O—C₁₋₄-alkylene-O—C₁₋₄-alkyl isdiethylenegly-coldimethylether.

More preferably, the organic solvent A is selected from the groupconsisting of C₄₋₈-cycloalkanone, C₁₋₄-alkyl-C(O)—C₁₋₄-alkyl,C₁₋₄-alkanoic acid C₁₋₄-alkyl ester, wherein the C₁₋₄-alkyl or theC₁₋₄-alkanoic acid can be substituted by hydroxyl or O—C₁₋₄-alkyl, andC₁₋₄-alkyl-O—C₁₋₄-alkylene-O—C₁₋₄-alkylene-O—C₁₋₄-alkyl, and mixturesthereof.

Most preferably, the organic solvent A is selected from the groupconsisting of C₅₋₆-cycloalkanone, C₁₋₄-alkanoic acid C₁₋₄-alkyl ester,and mixtures thereof. Even most preferably the organic solvent A iscyclopentanone or butyl acetate or mixtures thereof. In particularpreferred organic solvents A are butyl acetate or mixtures of butylacetate and pentanone, wherein the weight ratio of butylacetate/cyclopentane is at least from 99/1 to 20/80, more preferablyfrom 99/1 to 30/70.

If the photocurable polyimide A is applied as a solution in an organicsolvent A on the layer of the transistor or on the substrate, thephotocurable polyimide A can be applied by any possible solutionprocess, such as spin-coating, drop-casting or printing.

After applying photocurable polyimide A as a solution in an organicsolvent A on the layer of the transistor or on the substrate, a heattreatment at a temperature of below 140° C., for example at atemperature in the range of 60 to 120° C., preferably at a temperatureof below 120° C., for example in the range of 60 to 110° C. can beperformed.

The layer comprising photocurable polyimide A can have a thickness inthe range of 100 to 1000 nm, preferably, in the range of 300 to 1000 nm,more preferably 300 to 700 nm.

The layer comprising photocurable polyimide A can comprise from 50 to100% by weight, preferably from 80 to 100%, preferably 90 to 100% byweight of photocurable polyimide A based on the weight of the layercomprising photocurable polyimide A. Preferably, the layer comprisingphotocurable polyimide A essentially consists of photocurable polyimideA.

The layer comprising photocurable polyimide A can be irradiated with anysuitable light source providing light of a wavelength of >=360 nm, forexample with an LED lamp, in order to form the layer comprisingpolyimide B.

The layer comprising polyimide B can comprise from 50 to 100% by weight,preferably from 80 to 100%, preferably 90 to 100% by weight of polyimideB based on the weight of the layer comprising polyimide B. Preferably,the layer comprising polyimide B essentially consists of polyimide B.

The layer comprising photocurable polyimide B can have a thickness inthe range of 100 to 1000 nm, preferably, in the range of 300 to 1000 nm,more preferably 300 to 700 nm.

The irradiation of the layer comprising photocurable polyimide A withlight of a wave-length of >=360 nm in order to form the layer comprisingpolyimide B can be per-formed on only part of the layer comprisingphotocurable polyimide A, for example by using a mask.

If the irradiation of the layer comprising photocurable polyimide A withlight of a wave-length of >=360 nm in order to form the layer comprisingpolyimide B is performed on only part of the layer comprisingphotocurable polyimide A, the non-irradiated part of the polyimide canbe removed by dissolving it in an organic solvent B, leaving behind apatterned layer comprising polyimide B.

The organic solvent B can be any solvent (or solvent mixture) that candissolve at least 2% by weight, preferably at least 5% by weight, morepreferably, at least 8% by weight of the photocurable polyimide A basedon the weight of the solution of photocurable polyimide A.

The organic solvent B can be any solvent (or solvent mixture) that has aboiling point (at ambient pressure) of below 180° C., preferably below150° C., more preferably below 130° C.

Preferably, the organic solvent B is selected from the group consistingof N-methyl-pyrrolidone, C₄₋₈-cycloalkanone, C₁₋₄-alkyl-C(O)—C₁₋₄-alkyl,C₁₋₄-alkanoic acid C₁₋₄-alkyl ester, wherein the C₁₋₄-alkyl or theC₁₋₄-alkanoic acid can be substituted by hydroxyl or O—C₁₋₄-alkyl, andC₁₋₄-alkyl-O—C₁₋₄-alkylene-O—C₁₋₄-alkylene-O—C₁₋₄-alkyl, and mixturesthereof.

After dissolving the non-irradiated part of photocurable polyimide A inan organic sol-vent B, a heat treatment at a temperature of below 140°C., for example at a temperature in the range of 60 to 120° C.,preferably at a temperature of below 120° C., for example in the rangeof 60 to 110° C. can be performed.

The transistor on a substrate is preferably a field-effect transistor(FET) on a substrate and more preferably an organic field-effecttransistor (OFET) on a substrate.

Usually, an organic field effect transistor comprises a dielectric layerand a semiconducting layer. In addition, on organic field effecttransistor usually comprises a gate electrode and source/drainelectrodes.

An organic field effect transistor on a substrate can have variousdesigns.

The most common design of a field-effect transistor on a substrate isthe Bottom-Gate Bottom-Contact (BGBC) design. Here, the gate is on topof the substrate and at the bottom of the dielectric layer, thesemiconducting layer is at the top of the dielectric layer and thesource/drain electrodes are on top of the semiconducting layer.

Another design of a field-effect transistor on a substrate is theTop-Gate Bottom-Contact (TGBC) design. Here, the source/drain electrodesare on top of the substrate and at the bottom of the semiconductinglayer, the dielectric layer is on top of the di-semiconducting layer andthe gate electrode is on top of the dielectric layer.

The semiconducting layer comprises a semiconducting material. Examplesof semi-conducting materials are semiconducting materials having p-typeconductivity (carrier: holes) and semiconducting materials having n-typeconductivity (carrier: electrons).

Examples of semiconductors having n-type conductivity areperylenediimides, naphtalenediimides and fullerenes.

Semiconducting materials having p-type conductivity are preferred.Examples of semi-conducting materials having p-type conductivity aremolecules such as as rubrene, tetracene, pentacene,6,13-bis(triisopropylethynyl)pentacene, diindenoperylene,perylenediimide and tetracyanoquinodimethane, and polymers such aspolythiophenes, in particular poly 3-hexylthiophene (P3HT),polyfluorene, polydiacetylene, poly 2,5-thienylene vinylene, polyp-phenylene vinylene (PPV) and polymers comprising repeating unitshaving a diketopyrrolopyrrole group (DPP polymers).

Preferably the semiconducting material is a polymer comprising unitshaving a diketopyrrolopyrrole group (DPP polymer).

Examples of DPP polymers and their synthesis are, for example, describedin U.S. Pat. No. 6,451,459 B1, WO 2005/049695, WO 2008/000664, WO2010/049321, WO 2010/049323, WO 2010/108873, WO 2010/115767, WO2010/136353 and WO 2010/136352.

Preferably, the DPP polymer comprises, preferably essentially consists,of a unit selected from the group consisting of

a polymer unit of formula

a copolymer unit of formula

a copolymer unit of formula

anda copolymer unit of formula

whereinn′ is 4 to 1000, preferably 4 to 200, more preferably 5 to 100,x′ is 0.995 to 0.005, preferably x′ is 0.2 to 0.8,y′ is 0.005 to 0.995, preferably y′ is 0.8 to 0.2, andx′+y′=1;r′ is 0.985 to 0.005,s′ is 0.005 to 0.985,t′ is 0.005 to 0.985,u′ is 0.005 to 0.985, andr′+s′+t′+u′=1;

A is a group of formula

-   -   wherein    -   a″ is 1, 2, or 3,    -   a″′ is 0, 1, 2, or 3,    -   b′ is 0, 1, 2, or 3,    -   b″ is 0, 1, 2, or 3,    -   c′ is 0, 1, 2, or 3,    -   c″ is 0, 1, 2, or 3,    -   d′ is 0, 1, 2, or 3,    -   d″ is 0, 1, 2, or 3,    -   with the proviso that b″ is not 0, if a″′ is 0;    -   R⁴⁰ and R⁴¹ are the same or different and are selected from the        group consisting of hydrogen, C₁-C₁₀₀alkyl, —COOR^(106″),        C₁-C₁₀₀alkyl which is substituted with one or more halogen,        hydroxyl, nitro, —CN, or C₆-C₁₈aryl and/or interrupted by —O—,        —COO—, —OCO—, or —S—; C₇-C₁₀₀arylalkyl, carbamoyl,        C₅-C₁₂cycloalkyl, which can be substituted one to three times        with C₁-C₈alkyl and/or C₁-C₈alkoxy, C₆-C₂₄aryl, in particular        phenyl or 1- or 2-naphthyl which can be substituted one to three        times with C₁-C₈alkyl, C₁-C₂₅thioalkoxy, and/or C₁-C₂₅alkoxy, or        pentafluorophenyl, wherein        -   R^(106″) is C₁-C₅₀alkyl, preferably C₄-C₂₅alkyl,    -   Ar¹, Ar^(1′), Ar², Ar^(2′), Ar³, Ar^(3′), Ar⁴ and Ar^(4′) are        independently of each other heteroaromatic, or aromatic rings,        which optionally can be condensed and/or substituted, preferably

-   -   wherein    -   one of X³ and X⁴ is N and the other is CR⁹⁹,        -   wherein R⁹⁹ is hydrogen, halogen, preferably F, or            C₁-C₂₅alkyl, preferably a C₄-C₂₅alkyl, which may optionally            be interrupted by one or more oxygen or sulphur atoms,            C₇-C₂₅arylalkyl, or C₁-C₂₅alkoxy,    -   R¹⁰⁴, R^(104′), R¹²³ and R^(123′) are independently of each        other hydrogen, halogen, preferably F, or C₁-C₂₅alkyl,        preferably a C₄-C₂₅alkyl, which may optionally be interrupted by        one or more oxygen or sulphur atoms, C₇-C₂₅arylalkyl, or        C₁-C₂₅alkoxy,    -   R¹⁰⁵, R^(105′), R¹⁰⁶ and R^(106′) are independently of each        other hydrogen, halogen, C₁-C₂₅alkyl, which may optionally be        interrupted by one or more oxygen or sulphur atoms;        C₇-C₂₅arylalkyl, or C₁-C₁₈alkoxy,    -   R¹⁰⁷ is C₇-C₂₅arylalkyl, C₆-C₁₈aryl; C₆-C₁₈aryl which is        substituted by C₁-C₁₈alkyl, C₁-C₁₈perfluoroalkyl, or        C₁-C₁₈alkoxy; C₁-C₁₈alkyl; C₁-C₁₈alkyl which is interrupted by        —O—, or —S—; or —COOR¹²⁴;        -   R¹²⁴ is C₁-C₂₅alkyl, preferably C₄-C₂₅alkyl, which may            optionally be interrupted by one or more oxygen or sulphur            atoms, C₇-C₂₅arylalkyl,    -   R¹⁰⁸ and R¹⁰⁹ are independently of each other H, C₁-C₂₅alkyl,        C₁-C₂₅alkyl which is substituted by E′ and/or interrupted by D′,        C₇-C₂₅arylalkyl, C₆-C₂₄aryl, C₆-C₂₄aryl which is substituted by        G, C₂-C₂₀heteroaryl, C₂-C₂₀heteroaryl which is substituted by G,        C₂-C₁₈alkenyl, C₂-C₁₈alkynyl, C₁-C₁₈alkoxy, C₁-C₁₈alkoxy which        is substituted by E′ and/or interrupted by D′, or C₇-C₂₅aralkyl,    -   or    -   R¹⁰⁸ and R¹⁰⁹ together form a group of formula ═CR¹¹⁰R¹¹¹,        wherein        -   R¹¹⁰ and R¹¹¹ are independently of each other H, C₁-C₁₈alkyl            which is substituted by E′ and/or interrupted by D′,            C₆-C₂₄aryl, C₆-C₂₄aryl which is substituted by G, or            C₂-C₂₀heteroaryl, or C₂-C₂₀heteroaryl which is substituted            by G,    -   or    -   R¹⁰⁸ and R¹⁰⁹ together form a five or six membered ring, which        optionally can be substituted by C₁-C₁₈alkyl, C₁-C₁₈alkyl which        is substituted by E′ and/or interrupted by D′, C₆-C₂₄aryl,        C₆-C₂₄aryl which is substituted by G, C₂-C₂₀heteroaryl,        C₂-C₂₀heteroaryl which is substituted by G, C₂-C₁₈alkenyl,        C₂-C₁₈alkynyl, C₁-C₁₈alkoxy, C₁-C₁₈alkoxy which is substituted        by E′ and/or interrupted by D′, or C₇-C₂₅aralkyl, wherein        -   D′ is —CO—, —COO—, —S—, —O—, or —NR¹¹²—,        -   E′ is C₁-C₈thioalkoxy, C₁-C₈alkoxy, CN, —NR¹¹²R¹¹³,            —CONR¹¹²R¹¹³, or halogen,        -   G is E′, or C₁-C₁₈alkyl, and            -   R¹¹² and R¹¹³ are independently of each other H;                C₆-C₁₈aryl; C₆-C₁₈aryl which is substituted by                C₁-C₁₈alkyl, or C₁-C₁₈alkoxy; C₁-C₁₈alkyl; or                C₁-C₁₈alkyl which is interrupted by —O— and

B, D and E are independently of each other a group of formula

or a group of formula (24),with the proviso that in case B, D and E are a group of formula (24),they are different from A, wherein

-   -   k′ is 1,    -   l′ is 0, or 1,    -   r′ is 0, or 1,    -   z′ is 0, or 1, and    -   Ar¹, Ar⁶, Ar⁷ and Ar⁸ are independently of each other a group of        formula

-   -   wherein one of X⁵ and X⁶ is N and the other is CR¹⁴⁰,    -   R¹⁴⁰, R^(140′), R¹⁷⁰ and R^(170′) are independently of each        other H, or a C₁-C₂₅alkyl, preferably C₆-C₂₅alkyl, which may        optionally be interrupted by one or more oxygen atoms.

Preferred polymers are described in WO2010/049321.

Ar¹ and Ar² are preferably

very preferably

and most preferably

Ar², Ar^(2′), Ar³, Ar^(3′), Ar⁴ and Ar^(4′) are preferably

more preferably

The group of formula

is preferably

more preferably

most preferred

R⁴⁰ and R⁴¹ are the same or different and are preferably selected fromhydrogen, C₁-C₁₀₀alkyl, more preferably a C₈-C₃₆alkyl.

A is preferably selected from the group consisting of

Examples of preferred DPP polymers comprising, preferably consistingessentially of, a polymer unit of formula (20) are shown below:

whereinR⁴⁰ and R⁴¹ are C₁-C₃₆alkyl, preferably C₈-C₃₆alkyl, andn′ is 4 to 1000, preferably 4 to 200, more preferably 5 to 100.

Examples of preferred DPP polymers comprising, preferably consistingessentially of, a copolymer unit of formula (21) are shown below:

whereinR⁴⁰ and R⁴¹ are C₁-C₃₆alkyl, preferably C₈-C₃₆alkyl, andn′ is 4 to 1000, preferably 4 to 200, more preferably 5 to 100.

Examples of preferred DPP polymers comprising, preferably essentiallyconsisting of, a copolymer unit of formula (22) are shown below:

whereinR⁴⁰ and R⁴¹ are C₁-C₃₆alkyl, preferably C₈-C₃₆alkyl,R⁴² is C₁-C₁₈alkyl,R¹⁵⁰ is a C₄-C₁₈alkyl group,X′=0.995 to 0.005, preferably x′=0.4 to 0.9,y′=0.005 to 0.995, preferably y′=0.6 to 0.1, andx+y=1.

DPP Polymers comprising, preferably consisting essentially of, acopolymer unit of formula (22-1) are more preferred than DPP polymerscomprising, preferably consisting essentially of, a copolymer unit offormula (22-2).

The DPP polymers preferably have a weight average molecular weight of4,000 Daltons or greater, especially 4,000 to 2,000,000 Daltons, morepreferably 10,000 to 1,000,000 and most preferably 10,000 to 100,000Daltons.

DPP Polymers comprising, preferably consisting essentially of, acopolymer unit of formula (21-1) are particularly preferred. Referenceis, for example made to example 1 of WO2010/049321:

The dielectric layer comprises a dielectric material. The dielectricmaterial can be silicium/silicium dioxide, or, preferably, an organicpolymer such as poly(methyl-methacrylate) (PMMA), poly(4-vinylphenol)(PVP), poly(vinyl alcohol) (PVA), anzocyclobutene (BCB), and polyimide(PI).

Preferably the layer comprising the polyimide B is the dielectric layer.

The substrate can be any suitable substrate such as glass, or a plasticsubstrate. Preferably the substrate is a plastic substrate such aspolyethersulfone, polycarbonate, polysulfone, polyethylene terephthalate(PET) and polyethylene naphthalate (PEN). More preferably, the plasticsubstrate is a plastic foil.

Also part of the invention is a transistor obtainable by above process.

The advantage of the process for the preparation of a transistor,preferably an organic field effect transistor comprising a layercomprising polyimide B, for example as dielectric layer, is that allsteps of the process, and in particular the step of forming the layercomprising the photocurable polyimide A, can be performed at atemperatures below 160° C., preferably below 150°, more preferably below120° C.

Another advantage of the process of the present invention is that thephotocurable polyimide A used is resistant to shrinkage.

Another advantage of the process of the present invention is that thephotocurable polyimide A preferably has a glass temperature of at least150° C., preferably of at least 170° C. Thus, photocurable polyimide Aand polyimide B (derived from photocurable polyimide A) show a highchemical and thermal stability. As a consequence, the process of thepresent invention can be used to prepare, for example, an organic fieldeffect transistor, wherein the layer comprising polyimide B is thedielectric layer, wherein the electrodes on top of the dielectric layercan be structured by an etching process.

Another advantage of the process of the present invention is that thephotocurable polyimide A allows the formation of patterns.

Another advantage of the process of the present invention is thatphotocurable polyimide A is soluble in an organic solvent (solvent A).Preferably, it is possible to prepare a 2% by weight, more preferably a5% by weight and most preferably a 8% by weight solution of photocurablepolyimide A in the organic solvent. Thus, it is possible to applyphotocurable polyimide A by solution processing techniques.

Another advantage of the process of the present invention is that theorganic solvent used to dissolve photocurable polyimide A

-   -   (i) preferably has a boiling point (at ambient pressure) of        below 160° C., preferably below 150° C., more preferably below        120° C., and thus can be can be removed by heat treatment at a        temperature of below 120° C., preferably at a temperature in the        range of 60 to 110° C., and    -   (ii) preferably does not dissolve suitable semiconducting        materials such as diketopyrrolopyrol (DPP) thiophenes, and thus        allows the formation of a smooth border when applying the        photocurable polyimide A on a semiconducting layer comprising        diketopyrrolopyrol (DPP) thiophenes.

Another advantage of the process of the present invention is that allsteps of the process can be performed at ambient atmosphere, which meansthat no special precautions such as nitrogen atmosphere are necessary.

The advantage of the transistor of the present invention, preferably,wherein the transistor is an organic field effect transistor and whereinthe layer comprising polyimide B is the dielectric layer and thesemiconducting layer comprises a semiconducting material, for example adiketopyrrolopyrrole (DPP) thiophene polymer, is that the transistorshows a high mobility, a high Ion/Ioff ratio and a low gate leakage.

FIGS. 1 and 2 show pictures of the patterned layer of example 4comprising a polyimide derived from polyimide A6.

In FIG. 3 the leakage current density J in relation to the electricfield E for the capacitor of example 5 comprising a polyimide derivedfrom polyimide A¹ is shown.

In FIG. 4 the leakage current density J in relation to the electricfield E for the capacitor of example 5 comprising a polyimide derivedfrom polyimide A2 is shown.

In FIG. 5 the leakage current density J in relation to the electricfield E for the capacitor of example 6 comprising a polyimide derivedfrom polyimide A6 is shown.

In FIG. 6 the drain current I_(ds) in relation to the gate voltageV_(gs) (transfer curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 8 comprising a polyimide derived frompolyimide A1 at a source drain voltage V_(sd) of −1 V (squares),respectively, −20 V (triangles) is shown.

In FIG. 7 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 8 comprising a polyimide derived frompolyimide A1 at a gate voltage V_(gs) of 0 V (first and top curve, lighttriangles), −5 V (second curve), −10 V (third curve), −15 V (fourthcurve) and −20 V (fifth and bottom curve) is shown.

In FIG. 8 the drain current I_(ds) in relation to the gate voltageV_(gs) (transfer curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 9 comprising a polyimide derived frompolyimide A2 at a source drain voltage V_(sd) of −1 V (squares),respectively, −20 V (triangles) is shown.

In FIG. 9 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 9 comprising a polyimide derived frompolyimide A2 at a gate voltage V_(gs) of 0 V (first and top curve, lighttriangles), −5 V (second curve), −10 V (third curve), −15 V (fourthcurve) and −20 V (fifth and bottom curve) is shown.

In FIG. 10 the drain current I_(ds) in relation to the gate voltageV_(gs) (transfer curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 10 comprising a polyimide derived frompolyimide A6 at a source drain voltage V_(sd) of −1 V (squares),respectively, −20 V (triangles) is shown.

In FIG. 11 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 10 comprising a polyimide derived frompolyimide A6 at a gate voltage V_(gs) of 0 V (first and top curve, lighttriangles), −5 V (second curve), −10 V (third curve), −15 V (fourthcurve) and −20 V (fifth and bottom curve) is shown.

FIG. 12 shows the bottom-gate, bottom-contact (BGBC) field effecttransistor of example 12 comprising a layer comprising the polyimidederived from polyimide A2 (“P2 layer” in FIG. 12).

In FIG. 13 the drain current I_(ds) in relation to the gate voltageV_(g), (transfer curve) for the bottom-gate, bottom-contact (BGBC) fieldeffect transistor of example 12 comprising a polyimide derived frompolyimide A2 at a source drain voltage V_(sd) of −1 V, respectively, −15V is shown.

In FIG. 14 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the bottom-gate, bottom-contact (BGBC) fieldeffect transistor of example 12 comprising a polyimide derived frompolyimide A2 at a gate voltage V_(gs) of −10 V and −20 V is shown.

EXAMPLES Example 1 Synthesis of Polyimides A1 to A8 (PI A1 to A8)

A 50 mL reactor with anchor stirrer and nitrogen inlet is charged with asolution of diamine (9.8 mmol) in N-methylpyrrolidone (NMP) (20 mL).Dianhydride (10 mmol) is added and the reaction mixture is stirred for 6hours at room temperature. Butylamine (0.5 mL) is added and the reactionmixture is stirred for additional 2 hours. Acetic anhydride (3 mL) andtriethylamine (1 mL) are added and the mixture is stirred for additional16 hours. A blender beaker is filled with water (500 mL) and thereaction mixture is added slowly to the heavily blended water. Theprecipitated polyimide (PI) is collected by filtration, washed withwater and re-suspended in water (100 mL) for 1 hour. The polyimide (PI)is again collected by filtration and washed with water and then dried invacuum at 150° C. over night.

The diamine, respective the mixture of diamines, and the dianhydride,respectively the mixture of dianhydrides, can be derived from table 1.

TABLE 1 Tg (PI A) BuAc/CP^(h) PI A Dianhydride Diamine [° C.] [w/w] PIA1 BTDA^(a) MDMA^(c) 323 1:9 PI A2 BTDA^(a) MDEA^(d) 280 5:5 PI A3BTDA^(a) MDEA^(d)/DABM^(e) 275 3:7 80/20 (mol/mol) PI A4 BTDA^(a)MDEA^(d)/HMDA^(f) 200 5:5 50/50 (mol/mol) PI A5 BTDA^(a)MDEA^(d)/HMDA^(f) 240 4:6 80/20 (mol/mol) PI A6 BTDA^(a)MDEA^(d)/SiDA^(g) 180 9:1 50/50 (mol/mol) PI A7 BTDA^(a)MDEA^(d)/SiDA^(g) 220 7:3 80/20 (mol/mol) PI A8 BTDA^(a/)BPTDA^(b)MDEA^(d) 260 5:5 50/50 (mol/mol) ^(a)BTDA =3,3′,4,4′-benzophenonetetracarboxylic dianhydride (1a), ^(b)BPTDA =3,3′,4,4′-biphenyltetracarboxylic dianhydride (11a1), ^(c)MDMA =4,4′-methylene-bis(2,6-dimethylaniline), ^(d)MDEA =4,4′-methylenebis(2,6-diethylaniline) (5a5), ^(e)DABM =3,5-diaminobenzoic acid methyl ester (14a3), ^(f)HMDA =hexamethylenediamine (16a1), ^(g)SiDA =1,3-bis-(aminopropyl)tetramethyldisiloxane of formula (16b1),^(h)Composition comprising 10% by weight of the polyimides A1 to A8 inthe following solvents are prepared: 100% butyl acetate, 90% by weightbutylacetate (BuAc) and 10% by weight cyclopentanone (CP), 80% by weightbutylacetate and 20% by weight cyclopentanone, 70% by weightbutylacetate and 30% by weight cyclopentanone, 60% by weightbutylacetate and 40% by weight cyclopentanone, 50% by weightbutylacetate and 50% by weight cyclopentanone, 40% by weightbutylacetate and 60% by weight cyclopentanone, 30% by weightbutylacetate and 70% by weight cyclopentanone, 20% by weightbutylacetate and 80% by weight cyclopentanone, 10% by weightbutylacetate and 90% by weight cyclopentanone. The solvent with thehighest content of butyl acetate of the composition of the respectivepolyimide, which composition is a solution, is depicted in the column.

Example 2 Preparation of a Patterned Layer Comprising a PolyimideDerived from Polyimide A1

A 5% (weight/weight) solution of polyimide A1 of example 1 inN-methylpyrrolidone is filtered through a 0.45 μm filter and applied ona clean glass substrate by spin coating (2000 rpm, 45 seconds). The wetfilm is pre-baked at 100° C. for 60 seconds on a hot plate and thenphotocured with an LED lamp (365 nm, 10 mW/cm²) through a mask for 45seconds. The patterning is done by dipping the coated glass intoN-methyl-pyrrolidone for 60 seconds, followed by drying under nitrogenand post-baking at 100° C. for 30 seconds. A patterned layer comprisinga polyimide derived from polyimide A1 with a thickness of 400 nm isobtained.

Example 3 Preparation of a Patterned Layer Comprising a PolyimideDerived from Polyimide A2

A 6% (weight/weight) solution of polyimide A2 of example 1 incyclopentanone is filtered through a 0.45 μm filter and applied on aclean glass substrate by spin coating (3000 rpm, 60 seconds). The wetfilm is pre-baked at 100° C. for 60 seconds on a hot plate and thenphotocured by irradiation with an LED lamp (365 nm, 10 mW/cm²) through amask for 45 seconds. The patterning is done by dipping the coated glassinto N-methylpyrrolidone for 60 seconds, followed by drying undernitrogen and post-baking at 100° C. for 30 seconds. A patterned layercomprising a polyimide derived from polyimide A2 with a thickness of 600nm is obtained.

Example 4 Preparation of a Patterned Layer Comprising a PolyimideDerived from Polyimide A6

A 13% (weight/weight) solution of polyimide A6 of example 1 in butylacetate/cyclo-pentanone 80/20 (weight/weight) is filtered through a 0.45μm filter and applied on a clean glass substrate by spin coating (5200rpm, 60 seconds). The wet film is photocured with an LED lamp (365 nm,10 mW/cm²) through a mask for 3 minutes. The patterning is done bydipping the coated glass into cyclopentanone for 60 seconds, followed bydrying under nitrogen. A patterned layer comprising a polyimide derivedfrom polyimide A6 with a thickness of 610 nm is obtained.

FIGS. 1 and 2 show pictures of the patterned layer of example 4comprising a polyimide derived from polyimide A6.

Example 5 Preparation of a Capacitor Comprising a Layer Comprising aPolyimide Derived from Polyimide A1, Respectively, a Polyimide Derivedfrom Polyimide A2

A 6% (weight/weight) solution of polyimide A1, respectively, ofpolyimide A2 of example 1 in cyclopentanone is filtered through a 0.45μm filter and applied on a clean glass substrate with indium tin oxide(ITO) electrodes by spin coating (4200 rpm, 60 seconds). The wet film ispre-baked at 100° C. for 60 seconds on a hot plate and then photocuredwith an LED lamp (365 nm, 10 mW/cm²) through a mask for 3 minutes toobtain a 500 nm thick layer comprising a polyimide derived frompolyimide A1, respectively, a polyimide derived from polyimide A2. Goldelectrodes (area=0.785 mm²) are then vacuum-deposited through a shadowmask on the layer comprising the polyimide derived from polyimide A1,respectively, the polyimide derived from polyimide A2 at <1×10⁻⁶ Torr.

Example 6 Preparation of a Capacitor Comprising a Layer Comprising aPolyimide Derived from Polyimide A6

A 13% (weight/weight) solution of polyimide A6 of example 1 in butylacetate/cyclo-pentanone 80/20 (weight/weight) is filtered through a 0.45μm filter and applied on a clean glass substrate with indium tin oxide(ITO) electrodes by spin coating (4200 rpm, 60 seconds). The wet film ispre-baked at 100° C. for 60 seconds on a hot plate and then photocuredwith an LED lamp (365 nm, 10 mW/cm²) through a mask for 3 minutes toobtain a 900 nm thick layer of a polyimide derived from polyimide A6.Gold electrodes (area=0.785 mm²) are then vacuum-deposited through ashadow mask on the layer comprising the polyimide derived from polyimideA6 at <1×10⁻⁶ Torr.

Example 7 Measurement of the Leakage Current Density J [A/cm²] inRelation to the Electric Field E [MV/cm] for a Capacitor Comprising aPolyimide Derived from Polyimide A1, A2, Respectively, A6

The leakage current density J in relation to the electric field E forthe capacitor comprising a polyimide derived from polyimide A1, A2,respectively, A6 of example 5, respectively, example 6 is determined asfollows:

The J/E curves are calculated from IN curves knowing that E=V/d where dis the thickness of the dielectric film and that J=I/S where I is theleakage current measured between both electrodes and S is the surface ofthe gold electrode evaporated on top of the polyimide film. The INcurves are measured with an Agilent 4155C parameter analyzer in therange +100 V to −100V. The IN curves for positive voltages are measuredfrom 0 to +100V in 2 V steps on one half of the electrodes. The INcurves for negative voltages are measured from 0 to −100V in −2 V stepson the other half of the electrodes. The source electrode is connectedwith the indium tin oxide (ITO) electrode and the gate electrode withthe potential with the gold electrode.

In FIG. 3 the leakage current density J in relation to the electricfield E for the capacitor of example 5 comprising a polyimide derivedfrom polyimide A1 is shown.

In FIG. 4 the leakage current density J in relation to the electricfield E for the capacitor of example 5 comprising a polyimide derivedfrom polyimide A2 is shown.

In FIG. 5 the leakage current density J in relation to the electricfield E for the capacitor of example 6 comprising a polyimide derivedfrom polyimide A6 is shown.

As can be seen from FIGS. 1 to 3 the leakage current densities J ofcapacitors comprising a polyimide derived from polyimide A1, A2,respectively, A6 are very low, especially in the most relevant range ofthe electric field E, namely from −0.5 MV/cm to +0.5 MV/cm.

Example 8 Preparation of a Top-Gate, Bottom-Contact (TGBC) Field EffectTransistor Comprising a Layer Comprising a Polyimide Derived fromPolyimide A1

Gold is sputtered onto poly(ethylene terephthalate) (PET) foil to forman approximately 40 nm thick film and then source/drain electrodes(channel length: 10 μm; channel width: 10 mm) are structured byphotolithography process. A 0.75% (weight/weight) solution of Sepiolid™P1000 from BASF SE® (a diketopyrrolopyrrole (DPP)-thiophene-polymer) intoluene is filtered through a 0.45 μm polytetrafluoroethylene (PTFE)filter and then applied by spin coating (1400 rpm, 10.000 rpm/s, 15seconds). The wet Sepiolid™ P1000 film is dried at 100° C. on a hot platfor 30 seconds. A 6% (weight/weight) solution of polyimide A1 of example1 in cyclopentanone is filtered through a 0.45 μm filter and thenapplied by spin-coating (7200 rpm, 10.000 rpm/s, 60 seconds). The layercomprising polyimide A1 is pre-baked at 100° C. on a hot plate for 60seconds and then photocured using a Mask Aligner MA6 from SUSS (365 nm,5.5 mW/cm²) for 4 minutes to form a layer comprising a polyimide derivedfrom polyimide A1. Gate electrodes of gold (thickness approximately 120nm) are evaporated through a shadow mask on the layer comprising thepolyimide derived from polyimide A1. The whole process is performedwithout a protective atmosphere.

Example 9 Preparation of a Top-Gate, Bottom-Contact (TGBC) Field EffectTransistor Comprising a Layer Comprising a Polyimide Derived fromPolyimide A2

Gold is sputtered (thickness approximately 40 nm) onto poly(ethyleneterephthalate) (PET) foil and then source/drain electrodes (channellength: 10 μM; channel width: 10 mm) are structured by photolithographyprocess. A 0.75% (weight/weight) solution of Sepiolid™ P1000 from BASFSE® (a diketopyrrolopyrrole (DPP)-thiophene-polymer) in toluene isfiltered through a 0.45 μm polytetrafluoroethylene (PTFE) filter andthen applied by spin coating (1400 rpm, 10.000 rpm/s, 15 seconds). Thewet Sepiolid™ P1000 film is dried at 100° C. on a hot plat for 30seconds. A 6% (weight/weight) solution of polyimide A2 of example 1 incyclopentanone is filtered through a 0.45 μM filter and then applied byspin-coating (4200 rpm, 10.000 rpm/s, 60 seconds). The layer comprisingpolyimide A2 is pre-baked at 100° C. on a hot plate for 60 seconds andthen photocured using a Mask Aligner MA6 from SUSS (365 nm, 5.5 mW/cm²)for 4 minutes to form a layer comprising a polyimide derived frompolyimide A2. Gate electrodes of gold (thickness approximately 120 nm)are evaporated through a shadow mask on the layer comprising thepolyimide derived from polyimide A2. The whole process is performedwithout a protective atmosphere.

Example 10 Preparation of a Top-Gate, Bottom-Contact (TGBC) Field EffectTransistor Comprising a Layer Comprising a Polyimide Derived fromPolyimide A6

Gold is sputtered (thickness approximately 40 nm) onto poly(ethyleneterephthalate) (PET) foil and then source/drain electrodes (channellength: 10 μm; channel width: 10 mm) are structured by photolithographyprocess. A 0.75% (weight/weight) solution of Sepiolid™ P1000 from BASFSE® (a diketopyrrolopyrrole (DPP)-thiophene-polymer) in toluene isfiltered through a 0.45 μm polytetrafluoroethylene (PTFE) filter andthen applied by spin coating (1400 rpm, 10.000 rpm/s, 15 seconds). Thewet Sepiolid™ P1000 is dried at 100° C. on a hot plat for 30 seconds. A13% (weight/weight) solution of polyimide A6 of example 1 in butylacetate/cyclopentanone 80/20 (weight/weight) is filtered through a 0.45μm filter and then applied by spin-coating (5200 rpm, 10.000 rpm/s, 60seconds). The layer comprising polyimide A1 is pre-baked at 100° C. on ahot plate for 30 seconds and then photocured using a Mask Aligner MA6from SUSS (365 nm, 5.5 mW/cm²) for 6 minutes to form a layer comprisinga polyimide derived from polyimide A6. Gate electrodes of gold(thickness approximately 120 nm) are evaporated through a shadow mask onthe layer comprising a polyimide derived from polyimide A6. The wholeprocess is performed without a protective atmosphere.

Example 11 Measurement of the Characteristics of the Top-Gate,Bottom-Contact (TGBC) Field Effect Transistors of Examples 8 to 10

The characteristics of the top-gate, bottom-contact (TGBC) field effecttransistors of examples 8 to 10 are measured with a Keithley 2612Asemiconductor parameter analyzer.

In FIG. 6 the drain current I_(ds) in relation to the gate voltageV_(gs) (transfer curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 8 comprising a polyimide derived frompolyimide A1 at a source drain voltage V_(sd) of −1 V (squares),respectively, −20 V (triangles) is shown.

The top-gate, bottom-contact (TGBC) field effect transistor of example 8comprising a polyimide derived from polyimide A1 shows a mobility of0.16 cm²/Vs (calculated for the saturation regime) and an Ion/Ioff ratioof 5900. The gate leakage at source drain volt-age V_(sd) of 30 V isabout 3 orders of magnitudes below the source drain current I_(sd).

In FIG. 7 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 8 comprising a polyimide derived frompolyimide A1 at a gate voltage V_(gs) of 0 V (first and top curve, lighttriangles), −5 V (second curve), −10 V (third curve), −15 V (fourthcurve) and −20 V (fifth and bottom curve) is shown.

In FIG. 8 the drain current I_(ds) in relation to the gate voltageV_(gs) (transfer curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 9 comprising a polyimide derived frompolyimide A2 at a source drain voltage V_(sd) of −1 V (squares),respectively, −20 V (triangles) is shown.

The top-gate, bottom-contact (TGBC) field effect transistor of example 9comprising a polyimide derived from polyimide A2 shows a mobility of0.11 cm²/Vs (calculated for the saturation regime) and an Ion/Ioff ratioof 4600. The gate leakage at source drain volt-age V_(sd) of 30 V isabout 3 orders of magnitudes below the source drain current I_(sd).

In FIG. 9 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 9 comprising a polyimide derived frompolyimide A2 at a gate voltage V_(gs) of 0 V (first and top curve, lighttriangles), −5 V (second curve), −10 V (third curve), −15 V (fourthcurve) and −20 V (fifth and bottom curve) is shown.

In FIG. 10 the drain current I_(ds) in relation to the gate voltageV_(gs) (transfer curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 10 comprising a polyimide derived frompolyimide A6 at a source drain voltage V_(sd) of −1 V (squares),respectively, −20 V (triangles) is shown.

The top-gate, bottom-contact (TGBC) field effect transistor of example10 comprising a polyimide derived from polyimide A6 shows a mobility of0.22 cm²/Vs (calculated for the saturation regime) and an Ion/Ioff ratioof 2400. The gate leakage at source drain volt-age V_(sd) of 30 V isabout 2 orders of magnitudes below the source drain current I_(sd).

In FIG. 11 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the top-gate, bottom-contact (TGBC) fieldeffect transistor of example 10 comprising a polyimide derived frompolyimide A6 at a gate voltage V_(gs) of 0 V (first and top curve, lighttriangles), −5 V (second curve), −10 V (third curve), −15 V (fourthcurve) and −20 V (fifth and bottom curve) is shown.

Example 12 Preparation of a Bottom-Gate, Bottom-Contact (BGBC) FieldEffect Transistor Comprising a Layer Comprising a Polyimide Derived fromPolyimide A2

A 6% (weight/weight) solution of polyimide A2 of example 1 incyclopentanone is applied on a clean glass substrate with an indium tinoxide (ITO) (75 nm thick) gate electrode by spin coating (3000 rpm, 60seconds). The wet film is pre-baked at 100° C. for 60 seconds on a hotplate and then photocured using an LED lamp (365 nm, 10 mW/cm²) for 45seconds to form a layer comprising the polyimide derived from polyimideA2. A 4N gold layer (120 nm thick) is applied on the layer comprisingthe polyimide derived from polyimide A2. Drain/source electrodes arestructured by a photolithographic process (using a commercial positivephotoresist, etching the bare gold after development with KI/I₂ andremoving the remaining photoresist material with acetone) to form 24gold electrodes with various geometries (10, respectively, 20 μm channellength). Finally a 0.5% (weight/weight) solution of Sepiolid™ P1000 fromBASF SE® (a diketopyrrolopyrrole (DPP)-thiophene-polymer) in o-xylene isapplied by spin coating (3000 rpm, 50 seconds).

FIG. 12 shows the bottom-gate, bottom-contact (BGBC) field effecttransistor of example 12 comprising a layer comprising the polyimidederived from polyimide A2 (“P2 layer” in FIG. 12).

Example 13 Measurement of the Characteristics of the Bottom-Gate,Bottom-Contact (BGBC) Field Effect Transistor of Example 12

The characteristics of the bottom-gate, bottom-contact (BGBC) fieldeffect transistors of example 12 are measured with a Keithley 2612Asemiconductor parameter analyzer.

In FIG. 13 the drain current I_(ds) in relation to the gate voltageV_(gs) (transfer curve) for the bottom-gate, bottom-contact (BGBC) fieldeffect transistor of example 12 comprising a polyimide derived frompolyimide A2 at a source drain voltage V_(sd) of −1 V, respectively, −15V is shown.

In FIG. 14 the drain current I_(ds) in relation to the drain voltageV_(ds) (output curve) for the bottom-gate, bottom-contact (BGBC) fieldeffect transistor of example 12 comprising a polyimide derived frompolyimide A2 at a gate voltage V_(gs) of −10 V and −20 V is shown.

1) A process for the preparation of a transistor on a substrate, whichtransistor comprises a layer, which layer comprises polyimide B, whichprocess comprises the steps of i) forming a layer comprisingphotocurable polyimide A by applying photocurable polyimide A on a layerof the transistor or on the substrate ii) irradiating the layercomprising photocurable polyimide A with light of a wavelength of >=360nm in order to form the layer comprising polyimide B. 2) The process ofclaim 1, wherein the photocurable polyimide A is a polyimide which isobtainable by reacting a mixture of reactants, which mixture ofreactants comprise at least one dianhydride A, and at least one diamineA, wherein the dianhydride A is a dianhydride carrying at least onephotosensitive group and the diamine A is a diamine carrying at leastone crosslinkable group. 3) The process of claim 2, wherein thedianhydride A which is a dianhyride carrying at least one photosensitivegroup, is selected from the group consisting of

wherein R¹ is C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, halogen or phenyl g is 0, 1,2 or 3, preferably 0, X is a direct bond, CH₂, O, S or C(O), preferablyX is a direct bond, CH₂ or O. 4) The process of any of claims 2 to 3,wherein the diamine A, which is a diamine carrying at least onecrosslinkable group, is selected from the group consisting of (i) adiamine of formula

wherein R², R³ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkyl, n is 1, 2, 3 or 4 m is 0, 1, 2 or 3 provided n+m<=4, pis 0, 1, 2, 3 or 4, L¹ is O, S, C₁₋₁₀-alkylene, phenylene or C(O)wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S, (ii) a diamine of formula

wherein R⁴ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl R⁵ is O—C₁₋₁₀-alkyl,O—C₁₋₁₀-alkylene-O—C₁₋₁₀-alkyl, O—C₁₋₁₀-alkylene-N(C₁₋₁₀-alkyl)₂,N(C₁₋₁₀-alkyl)₂, O-phenyl, W, O—C₁₋₁₀-alkylene-W, O-phenylene-W,N(R⁶)(C₁₋₁₀-alkylene-W) or N(R⁶)(phenylene-W), wherein R⁶ is H,C₁₋₁₀-alkyl, C₄₋₁₀-cycloalkyl or C₁₋₁₀-alkylene-W, W is O—C₂₋₁₀-alkenyl,N(R⁷)(C₂₋₁₀-alkenyl), O—C(O)—CR⁸═CH₂, N(R⁷)(C(O)—CR⁸═CH₂), or

wherein R⁷ is H, C₁₋₁₀-alkyl, C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl orC(O)—CR⁸═CH₂, R⁸ is H, C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl, R⁹ is H,C₁₋₁₀-alkyl or C₄₋₈-cycloalkyl q is 1, 2, 3 or 4 o is 0, 1, 2, 3 q+o<=4,in case o is 0, R⁵ is W, O—C₁₋₁₀-alkylene-W, O-phenylene-W,N(R⁶)(C₁₋₁₀-alkylene-W) or N(R⁶)(phenylene-W), wherein C₁₋₁₀-alkylene,can be optionally substituted with one or more C₁₋₁₀-alkyl,C₁₋₁₀-haloalkyl, and/or C₄₋₈-cycloalkyl, or interrupted by O or S, and(iii) a diamine of formula

wherein R¹⁰ and R¹¹ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkyl R¹³ and R¹⁴ are the same and different and areC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, C₄₋₈-cycloalkyl, C₂₋₁₀-alkenyl,C₄₋₁₀-cycloalkenyl or phenyl, L² is C₁₋₁₀-alkylene or phenylene r is 0,1, 2, 3 or 4 s is 0, 1, 2, 3 or 4 r+s<=4 in case both r and s are 0 thenat least one of R¹³ and R¹⁴ is C₂₋₁₀-alkenyl or C₄₋₁₀-cycloalkenyl, t is0 or an integer from 0 to 50, preferably 0 or an integer from 0 to 25,more preferably 0 or an integer from 1 to 6, most preferably 0 or 1, uis 0 or 1 wherein C₁₋₁₀-alkylene can be optionally substituted with oneor more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, orinterrupted by O or S. 5) The process of claims 2 to 3, wherein thediamine A, which is a diamine carrying at least one crosslinkable group,is a diamine of formula

wherein R², R³ are the same or different and are H, C₁₋₁₀-alkyl orC₄₋₈-cycloalkyl, n is 1, 2, 3 or 4 m is 0, 1, 2 or 3 provided n+m<=4, pis 0, 1, 2, 3 or 4, L¹ is O, S, C₁₋₁₀-alkylene, phenylene or C(O)wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S. 6) The process of any of claims 2 to 5, wherein the mixture ofreactants comprises at least one dianhydride B and/or at least onediamine B, wherein the dianhydride B is a dianhydride carrying nophotosensitive group, and the diamine B is a diamine carrying nocrosslinkable group. 7) The process of claim 6, wherein dianhydride B,which is a dianhydride carrying no photosensitive group, is selectedfrom the group consisting of

wherein R¹² is C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl, halogen or phenyl h is 0,1, 2 or 3, preferably 0, Y is a C₁₋₁₀-alkylene, O or S, preferably Y isCH₂ or O. 8) The process of any of claims 6 and 7, wherein the diamineB, which is a diamine carrying no crosslinkable group, is selected fromthe group consisting of (i) a diamine of formula

wherein R¹⁵ is halogen or O—C₁₋₁₀-alkyl, d is 0, 1, 2, 3 or 4 v is 0, 1,2, 3 or 4, L³ is a direct bond, O, S, C₁₋₁₀-alkylene or CO, whereinC₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S, (ii) a diamine of formula

wherein R¹⁶ is halogen or O—C₁₋₁₀-alkyl R¹⁷ is O—C₁₋₁₀-alkyl,O—C₁₋₁₀-alkylene-O—C₁₋₁₀-alkyl, O-phenyl,O—C₁₋₁₀-alkylene-N(C₁₋₁₀-alkyl)₂ or N(C₁₋₁₀-alkyl)₂ w is 0, 1, 2 or 3 xis 1, 2, 3, 4 w+x<=4, wherein C₁₋₁₀-alkylene can be optionallysubstituted with one or more C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/orC₄₋₈-cycloalkyl, or interrupted by O or S, (iii) a diamine of formula

wherein R¹⁸ is halogen or O—C₁₋₁₀-alkyl, R¹⁹ and R²⁰ are the same anddifferent and are C₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl or C₄₋₈-cycloalkyl orphenyl, L³ is C₁₋₁₀-alkylene or phenylene y is 0, 1, 2, 3 or 4 z is 0 or1 a is 0 or an integer from 1 to 50, preferably 0 or an integer from 1to 25, more preferably 0 or an integer from 1 to
 6. most preferably 0 or1, wherein C₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S, and (iv) a diamine of formula

wherein R²¹ and R²² are the same and different and are C₁₋₁₀-alkyl,C₁₋₁₀-haloalkyl or C₄₋₈-cycloalkyl, L⁴ is C₁₋₁₀-alkylene,C₄₋₈-cycloalkylene or C₄₋₈-cycloalkylene-Z—C₄₋₈-cycloalkylene, wherein Zis C₁₋₁₀-alkylene, S, O or CO b is 0 or 1 c is 0 or an integer from 1 to50, preferably, 0 or an integer from 1 to 25, more preferably 0 or aninteger from 1 to 6, most preferably 0 or 1, e is 0 or 1 whereinC₁₋₁₀-alkylene can be optionally substituted with one or moreC₁₋₁₀-alkyl, C₁₋₁₀-haloalkyl and/or C₄₋₈-cycloalkyl, or interrupted by Oor S. 9) The process of any of claims 1 to 8, wherein the photocurablepolyimide A is applied as a solution in an organic solvent A on a layerof the transistor or on the substrate. 10) The process of claim 9,wherein the organic solvent A is selected from the group consisting ofN-methylpyrrolidone, C₄₋₈-cycloalkanone, C₁₋₄-alkyl-C(O)—C₁₋₄-alkyl,C₁₋₄-alkanoic acid C₁₋₄-alkyl ester, wherein the C₁₋₄-alkyl or theC₁₋₄-alkanoic acid can be substituted by hydroxyl or O—C₁₋₄-alkyl, andC₁₋₄-alkyl-O—C₁₋₄-alkylene-O—C₁₋₄-alkylene-O—C₁₋₄-alkyl, and mixturesthereof. 11) The process of claim 10, wherein the organic solvent A isbutyl acetate or mixtures of butyl acetate and cyclopentanone, whereinthe weight ratio of butyl acetate/cyclopentane is at least from 99/1 to20/80, more preferably from 99/1 to 30/70. 12) The process of any ofclaims 1 to 11, wherein the transistor on a substrate is an organicfield-effect transistor (OFET), which comprises, in addition to thelayer comprising polyimide B, a layer comprising a semiconductingmaterial. 13) The process of claim 12, wherein the semiconductingmaterial is a polymer comprising units having a diketopyrrolopyrrolegroup (DPP polymer). 14) The process of claim 13, wherein the DPPpolymer comprises, preferably essentially consists, of a unit selectedfrom the group consisting of a polymer unit of formula

a copolymer unit of formula

a copolymer unit of formula

and A copolymer unit of formula

wherein n′ is 4 to 1000, preferably 4 to 200, more preferably 5 to 100,x′ is 0.995 to 0.005, preferably x′ is 0.2 to 0.8, y′ is 0.005 to 0.995,preferably y′ is 0.8 to 0.2, and x′+y′=1; r′ is 0.985 to 0.005, s′ is0.005 to 0.985, t′ is 0.005 to 0.985, u′ is 0.005 to 0.985, andr′+s′+=1; A is a group of formula

wherein a″ is 1, 2, or 3, a″′ is 0, 1, 2, or 3, b′ is 0, 1, 2, or 3, b″is 0, 1, 2, or 3, c′ is 0, 1, 2, or 3, c″ is 0, 1, 2, or 3, d′ is 0, 1,2, or 3, d″ is 0, 1, 2, or 3, with the proviso that b″ is not 0, if a′″is 0; R⁴⁰ and R⁴¹ are the same or different and are selected from thegroup consisting of hydrogen, C₁-C₁₀₀alkyl, —COOR^(106″), C₁-C₁₀₀alkylwhich is substituted with one or more halogen, hydroxyl, nitro, —CN, orC₆-C₁₈aryl and/or interrupted by —O—, —COO—, −OCO—, or —S—;C₇-C₁₀₀arylalkyl, carbamoyl, C₅-C₁₂cycloalkyl, which can be substitutedone to three times with C₁-C₈alkyl and/or C₁-C₈alkoxy, C₆-C₂₄aryl, inparticular phenyl or 1- or 2-naphthyl which can be substituted one tothree times with C₁-C₈alkyl, C₁-C₂₅thioalkoxy, and/or C₁-C₂₅alkoxy, orpentafluorophenyl, wherein R^(106″) is C₁₀-C₅₀alkyl, preferablyC₄-C₂₅alkyl, Ar¹, Ar^(1′), Ar², Ar^(2′), Ar³, Ar^(3′), Ar⁴ and Ar^(4′)are independently of each other heteroaromatic, or aromatic rings, whichoptionally can be condensed and/or substituted, preferably

wherein one of X³ and X⁴ is N and the other is CR⁹⁹, wherein R⁹⁹ ishydrogen, halogen, preferably F, or C₁-C₂₅alkyl, preferably aC₄-C₂₅alkyl, which may optionally be interrupted by one or more oxygenor sulphur atoms, C₇-C₂₅arylalkyl, or C₁-C₂₅alkoxy, R¹⁰⁴, R^(104′), R¹²³and R^(123′) are independently of each other hydrogen, halogen,preferably F, or C₁-C₂₅alkyl, preferably a C₄-C₂₅alkyl, which mayoptionally be interrupted by one or more oxygen or sulphur atoms,C₇-C₂₅arylalkyl, or C₁-C₂₅alkoxy, R¹⁰⁵, R^(105′), R¹⁰⁶ and R^(106′) areindependently of each other hydrogen, halogen, C₁-C₂₅alkyl, which mayoptionally be interrupted by one or more oxygen or sulphur atoms;C₇-C₂₅arylalkyl, or C₁-C₁₈alkoxy, R¹⁰⁷ is C₇-C₂₅arylalkyl, C₆-C₁₈aryl;C₆-C₁₈aryl which is substituted by C₁-C₁₈alkyl, C₁-C₁₈perfluoroalkyl, orC₁-C₁₈alkoxy; C₁-C₁₈alkyl; C₁-C₁₈alkyl which is interrupted by —O—, or—S—; or —COOR¹²⁴; R¹²⁴ is C₁-C₂₅alkyl, preferably C₄-C₂₅alkyl, which mayoptionally be interrupted by one or more oxygen or sulphur atoms,C₇-C₂₅arylalkyl, R¹⁰⁸ and R¹⁰⁹ are independently of each other H,C₁-C₂₅alkyl, C₁-C₂₅alkyl which is substituted by E′ and/or interruptedby D′, C₇-C₂₅arylalkyl, C₆-C₂₄aryl, C₆-C₂₄aryl which is substituted byG, C₂-C₂₀heteroaryl, C₂-C₂₀heteroaryl which is substituted by G,C₂-C₁₈alkenyl, C₂-C₁₈alkynyl, C₁-C₁₈alkoxy, C₁-C₁₈alkoxy which issubstituted by E′ and/or interrupted by D′, or C₇-C₂₅aralkyl, or R¹⁰⁸and R¹⁰⁹ together form a group of formula ═CR¹¹⁰R¹¹¹, wherein R¹¹⁰ andR¹¹¹ are independently of each other H, C₁-C₁₈alkyl which is substitutedby E′ and/or interrupted by D′, C₆-C₂₄aryl, C₆-C₂₄aryl which issubstituted by G, or C₂-C₂₀heteroaryl, or C₂-C₂₀heteroaryl which issubstituted by G, or R¹⁰⁸ and R¹⁰⁹ together form a five or six memberedring, which optionally can be substituted by C₁-C₁₈alkyl, C₁-C₁₈alkylwhich is substituted by E′ and/or interrupted by D′, C₆-C₂₄aryl,C₆-C₂₄aryl which is substituted by G, C₂-C₂₀heteroaryl, C₂-C₂₀heteroarylwhich is substituted by G, C₂-C₁₈alkenyl, C₂-C₁₈alkynyl, C₁-C₁₈alkoxy,C₁-C₁₈alkoxy which is substituted by E′ and/or interrupted by D′, orC₇-C₂₅aralkyl, wherein D′ is —CO—, —COO—, —S—, —O—, or —NR¹¹²—, E′ isC₁-C₈thioalkoxy, C₁-C₈alkoxy, CN, —NR¹¹²R¹¹³, —CONR¹¹²R¹¹³, or halogen,G is E′, or C₁-C₁₈alkyl, and R¹¹² and R¹¹³ are independently of eachother H; C₆-C₁₈aryl; C₆-C₁₈aryl which is substituted by C₁-C₁₈alkyl, orC₁-C₁₈alkoxy; C₁-C₁₈alkyl; or C₁-C₁₈alkyl which is interrupted by —O—and B, D and E are independently of each other a group of formula

or a group of formula (24), with the proviso that in case B, D and E area group of formula (24), they are different from A, wherein k′ is 1, l′is 0, or 1, r′ is 0, or 1, z′ is 0, or 1, and Ar⁵, Ar⁶, Ar⁷ and A⁸ areindependently of each other a group of formula

wherein one of X⁵ and X⁶ is N and the other is CR¹⁴⁰, R¹⁴⁰, R^(140′),R¹⁷⁰ and R^(170′) are independently of each other H, or a C₁-C₂₅alkyl,preferably C₆-C₂₅alkyl, which may optionally be interrupted by one ormore oxygen atoms. 15) A transistor on a substrate obtainable by theprocess of any of claims 1 to 14.